Silicon oxide based high capacity anode materials for lithium ion batteries

ABSTRACT

Silicon oxide based materials, including composites with various electrical conductive compositions, are formulated into desirable anodes. The anodes can be effectively combined into lithium ion batteries with high capacity cathode materials. In some formulations, supplemental lithium can be used to stabilize cycling as well as to reduce effects of first cycle irreversible capacity loss. Batteries are described with surprisingly good cycling properties with good specific capacities with respect to both cathode active weights and anode active weights.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of copending U.S. patent applicationSer. No. 13/108,708 filed May 16, 2011 to Haixia Deng et al., entitled“Silicon Oxide Based High Capacity Anode Materials For Lithium IonBatteries” incorporated herein by reference.

GOVERNMENT RIGHTS

Development of the inventions described herein was at least partiallyfunded with government support through U.S. Department of Energy grantARPA-E-DE-AR0000034, and the U.S. government has certain rights in theinventions.

FIELD OF THE INVENTION

The invention relates to high capacity negative electrode activematerials based on silicon oxide for lithium ion batteries. Theinvention further relates to batteries formed with silicon and/orsilicon oxide based negative electrode active materials and highcapacity lithium rich positive electrode active materials as well as tosilicon and/or silicon oxide-based lithium ion batteries with asupplemental lithium source.

BACKGROUND

Lithium batteries have been used in various applications due to theirhigh energy density. For some current commercial batteries, the negativeelectrode material can be graphite, and the positive electrode materialscan comprise of lithium cobalt oxide (LiCoO₂), lithium manganese oxide(LiMn₂O₄), lithium iron phosphate (LiFePO₄), lithium nickel oxide(LiNiO₂), lithium nickel cobalt oxide (LiNiCoO₂), lithium nickel cobaltmanganese oxide (LiNiMnCoO₂), lithium nickel cobalt aluminum oxide(LiNiCoAlO₂) and the like. For negative electrodes, lithium titanate isan alternative to graphite with good cycling properties, but it has alower energy density. Other alternatives to graphite, such as tin oxideand silicon, have the potential for providing increased energy density.However, some high capacity negative electrode materials have been foundto be unsuitable commercially due to high irreversible capacity loss andpoor discharge and recharge cycling related to structural changes andanomalously large volume expansions, especially for silicon, that areassociated with lithium intercalation/alloying. The structural changesand large volume changes can destroy the structural integrity of theelectrode, thereby decreasing the cycling efficiency.

New positive electrode active materials are presently under developmentthat can significantly increase the corresponding energy density andpower density of the corresponding batteries. Particularly promisingpositive electrode active materials are based on lithium richlayered-layered compositions. In particular, the improvement of batterycapacities can be desirable for vehicle applications, and for vehicleapplications the maintenance of suitable performance over a large numberof charge and discharge cycles is important.

SUMMARY OF THE INVENTION

In a first aspect, the invention pertains to a lithium ion batterycomprising a positive electrode comprising a lithium metal oxide, anegative electrode, a separator between the positive electrode and thenegative electrode, and extractable supplemental lithium wherein thenegative electrode comprises silicon oxide based active material.

In a further aspect, the invention pertains to a lithium ion batterycomprising a positive electrode comprising a lithium metal oxide, anegative electrode, and a separator between the positive electrode andthe negative electrode, wherein the negative electrode comprises siliconoxide based active material. The negative electrode can comprise of apolymer binder having an elongation of at least about 50% withouttearing and a tensile strength of at least about 100 MPa.

In another aspect, the invention pertains to a lithium ion batterycomprising a positive electrode comprising a lithium metal oxide, anegative electrode comprising a silicon oxide based active material, anda separator between the positive electrode and the negative electrode,wherein after 50 charge-discharge cycles between 4.5V and 1.0V, thebattery exhibits at least about 750 mAh/g discharge capacity fromnegative electrode active material and at least about 150 mAh/gdischarge capacity from positive electrode active material at a rate ofC/3.

In additional aspects, the invention pertains to a composite compositioncomprising silicon oxide with the structure of SiO_(x), 0.1≦x≦1.9 andanode-inert elemental metal.

In other aspects, the invention pertains to a lithium ion batterycomprising a positive electrode comprising a lithium metal oxide, anegative electrode, a separator between the positive electrode and thenegative electrode, and an electrolyte comprising lithium ions and ahalogenated carbonate, wherein the negative electrode comprises siliconoxide based active material. The battery can exhibit a dischargecapacity that decreases by no more than about 15 percent at the 50thdischarge cycle relative to the 7th discharge cycle when discharged at arate of C/3 from the 7th discharge to the 50th discharge.

Furthermore, the invention pertains to a lithium ion battery comprisinga positive electrode comprising a lithium metal oxide, a negativeelectrode, and a separator between the positive electrode and thenegative electrode, wherein the negative electrode comprises siliconoxide based active material having a specific capacity of at least about1000 mAh/g at a rate of C/3 based on anode's mass.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic perspective view of a battery stack with acathode, an anode, and a separator between the cathode and anode.

FIG. 2 is a plot of charge/discharge profiles of pristine SiO in micronsize.

FIG. 3 shows cycling performance of pristine SiO in micron size atdifferent loading density.

FIG. 4 shows x-ray diffraction (XRD) measurements of SiO after differenttime periods of high-energy mechanical (HEMM) milling at 300 rpm.

FIG. 5 is incremental volume percent versus particle diameter graphshowing particle size distribution of SiO after different time periodsof high-energy mechanical milling (HEMM) at 300 rpm.

FIG. 6 shows cycling performance of SiO after different time periods ofHEMM milled at 300 rpm.

FIG. 7 shows x-ray diffraction (XRD) measurements of SiO after differentheating and coating treatment conditions.

FIG. 8 shows cycling performance of SiO after different heating andcoating treatment conditions.

FIG. 9 shows the effect of 10, 15, 20 volume % of fluorinatedelectrolyte additive (FEA) on Si-based electrode.

FIG. 10 shows effect of 10, 15, 20 volume % of fluorinated electrolyteadditive on SiO composite based electrode.

FIG. 11 shows effect of 10 volume % of fluorinated additive on HCMR™cathode material based electrode.

FIG. 12 shows x-ray diffraction measurements of SiO-graphite samplesafter different time periods of milling at 300 rpm.

FIG. 13 shows cycling performance of SiO-graphite composite at variedloading densities of 2.25-3.29 mg/cm².

FIG. 14 shows charge/discharge profile of a battery with SiO-graphitecomposite based anode and HCMR™ active material based cathode.

FIG. 15 shows cycling performance of a battery with SiO-Gr-HC compositebased anode and HCMR™ active material based cathode.

FIG. 16 shows the effect of supplemental lithium on charge/dischargeplots for SiO-based composite.

FIG. 17 shows XRD measurements of SiO-metal (SiO-M) and SiO-metal-carbonnano fiber (SiO-M-CNF) composites.

FIG. 18 shows cycling performances of batteries with SiO-M and SiO-M-CNFbased electrode and lithium metal counter electrode.

FIG. 19 shows cycling performance of a battery with SiO-M-CNF basedanode and HCMR™ cathode compared with a battery with lithium metal anodeand HCMR™ cathode.

FIG. 20 shows charge/discharge profile of a battery with SiO-M-CNF basedanode and HCMR™ cathode at different cycles.

FIG. 21 shows cycling performance of a battery with SiO-M-CNF basedanode and HCMR™ cathode.

FIG. 22 shows a graph of incremental volume percent versus particlediameter showing the particle diameter profiles of pristine SiO, SiO andSiO-M HEMM milled at 300 rpm, and SiO-M HEMM milled mixed with CNFfollowed by additional milling at 300 rpm.

FIG. 23 shows scanning electron microscopy (SEM) images of SiO-M-CNFcomposite at different magnifications.

FIG. 24 shows XRD measurements of SiO-Gr-HC—Si composite.

FIG. 25a shows cycling performance of SiO-Gr-HC—Si composite with orwithout carbon nano fibers.

FIG. 25b shows cycling performance of a battery with SiO-Gr-HC—Sicomposite based anode and HCMR™ cathode based upon the mass of thepositive electrode active material.

FIG. 25c shows cycling performance of SiO-Gr-HC—Si composites atdifferent compositions.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Silicon oxide based compositions have been formed into compositematerials with high capacities and very good cycling properties. Inparticular, oxygen deficient silicon oxides can be formed intocomposites with electrically conductive materials, such as conductivecarbons or metal powders, which surprisingly significantly improvecycling while providing for high values of specific capacity.Furthermore, the milling of the silicon oxides into smaller particles,such as submicron structured materials, can further improve theperformance of the materials. The silicon oxide based materials maintaintheir high capacities and good cycling as negative electrode activematerials when placed into lithium ion batteries with high capacitylithium metal oxide positive electrode active materials. The cycling canbe further improved with the addition of supplemental lithium into thebattery and/or with an adjustment of the balance of the active materialsin the respective electrodes. Supplemental lithium can replace at leastsome of the lithium lost to the irreversible capacity loss due to thenegative electrode and can stabilize the positive electrode with respectto cycling. Based on appropriate designs of the batteries, high energydensity batteries can be produced, and the batteries are suitable for arange of commercial applications.

As with silicon, oxygen deficient silicon oxide, e.g., silicon oxide,SiO_(x), 0.1≦x≦1.5, can intercalate/alloy with lithium such that theoxygen deficient silicon oxide can perform as an active material in alithium based battery. The oxygen deficient silicon oxide canincorporate a relatively large amount of lithium such that the materialcan exhibit a large specific capacity. However, silicon oxide isobserved generally to have a capacity that fades quickly with batterycycling, as is observed with elemental silicon. The composite materialsdescribed herein can significantly address the cycling fade of thesilicon oxide based materials. In particular, composites can be formedwith electrically conductive components that contribute to theconductivity of the electrode as well as the stabilization of thesilicon oxide during cycling.

Lithium has been used in both primary and secondary batteries. Anattractive feature of lithium metal for battery use is its light weightand the fact that it is the most electropositive metal, and aspects ofthese features can be advantageously captured in lithium-based batteriesalso. Certain forms of metals, metal oxides, and carbon materials areknown to incorporate lithium ions into its structure throughintercalation, alloying or similar mechanisms. The positive electrode ofa lithium based battery generally comprises an active material thatreversibly intercalates/alloys with lithium, e.g., a metal oxide.Lithium ion batteries generally refer to batteries in which the negativeelectrode active material is also a lithium intercalation/alloyingmaterial.

If elemental lithium metal itself is used as the anode or negativeelectroactive material, the resulting battery generally is referred toas a lithium battery. Lithium batteries can initially cycle with goodperformance, but dendrites can form upon lithium metal deposition thateventually can breach the separator and result in failure of thebattery. As a result, commercial lithium-based secondary batteries havegenerally avoided the deposition of lithium metal through the use of anegative electrode active material that operates throughintercalation/alloying or the like and with a slight excess in negativeelectrode capacity relative to the cathode or positive electrode tomaintain the battery from lithium plating on the anode. If the negativeelectrode comprises a lithium intercalation/alloying composition, thebattery can be referred to as a lithium ion battery.

The batteries described herein are lithium based batteries that use anon-aqueous electrolyte solution which comprises lithium ions. Forsecondary lithium ion batteries during charge, oxidation takes place inthe cathode (positive electrode) where lithium ions are extracted andelectrons are released. During discharge, reduction takes place in thecathode where lithium ions are inserted and electrons are consumed.Similarly, during charge, reduction takes place at the anode (negativeelectrode) where lithium ions are taken up and electrons are consumed,and during discharge, oxidation takes place at the anode with lithiumions and electrons being released. Unless indicated otherwise,performance values referenced herein are at room temperature. Asdescribed below some of the testing of the silicon oxide based activematerials is performed in lithium and lithium ion batteries. Generally,the lithium ion batteries are formed with lithium ions in the positiveelectrode material such that an initial charge of the battery transfersa significant fraction of the lithium from the positive electrodematerial to the negative electrode material to prepare the battery fordischarge.

The word “element” is used herein in its conventional way as referringto a member of the periodic table in which the element has theappropriate oxidation state if the element is in a composition and inwhich the element is in its elemental form, M⁰, only when stated to bein an elemental form. Therefore, a metal element generally is only in ametallic state in its elemental form or a corresponding alloy of themetal's elemental form. In other words, a metal oxide or other metalcomposition, other than metal alloys, generally is not metallic.

When lithium ion batteries are in use, the uptake and release of lithiumfrom the positive electrode and the negative electrode induces changesin the structure of the electroactive material. As long as these changesare essentially reversible, the capacity of the material does notchange. However, the capacity of the active materials is observed todecrease with cycling to varying degrees. Thus, after a number ofcycles, the performance of the battery falls below acceptable values,and the battery is replaced. Also, on the first cycle of the battery,generally there is an irreversible capacity loss that is significantlygreater than per cycle capacity loss at subsequent cycles. Theirreversible capacity loss (IRCL) is the difference between the chargecapacity of the new battery and the first discharge capacity. Theirreversible capacity loss results in a corresponding decrease in thecapacity, energy and power for the battery due to changes in the batterymaterials during the initial cycle.

The silicon oxide based materials exhibit a large irreversible capacityloss, as described further below. In some embodiments, the battery cancomprise supplemental lithium, which can compensate for the irreversiblecapacity loss of the silicon oxide based materials as well as tosurprisingly stabilize the cycling of the battery. The supplementallithium can replace some or all of the active lithium removed from thecycling as a result of the irreversible capacity loss of the siliconoxide based material. In a traditional lithium ion battery, the lithiumfor cycling is supplied only by a positive electrode active materialcomprising lithium. The battery is initially charged to transfer lithiumfrom the positive electrode to the negative electrode where it is thenavailable for discharge of the battery. Supplemental lithium resultsfrom a supply of active lithium other than the positive electrode activematerial. It has also been found that supplemental lithium can be veryeffective for the stabilization of lithium rich high capacity positiveelectrode active materials. See, copending U.S. patent application Ser.No. 12/938,073 now U.S. Pat. No. 9,166,222 to Amiruddin et al.,entitled, “Lithium Ion Batteries With Supplemental Lithium,”(hereinafter “the '073 patent application”) incorporated herein byreference. Thus, good cycling has been obtained for realistic lithiumion batteries with supplemental lithium to have relatively high specificcapacities. Supplemental lithium, for example, can be supplied byelemental lithium, lithium alloys, a sacrificial lithium source orthrough electrochemical lithiation of the negative electrode prior tocompletion of the ultimate battery.

Silicon oxide based materials with greater capacity upon cycling can beproduced through the milling of the silicon oxide to form smallerparticles. In further embodiments, the silicon oxide based materials canbe formed into composites with electrically conductive powders incombination with high energy mechanical milling (HEMM) or the like.Alternatively or additionally, the silicon oxide based materials can besubjected to high temperature heat treatment. Smaller silicon oxideparticles obtained from HEMM treatment has shown greater capacity ineither silicon oxide electrode or electrodes with composites of siliconoxide-conductive carbon particle, e.g., graphitic carbon, thancommercial silicon oxides with larger particle sizes. Pyrolytic carboncoated silicon oxide composites showed improved conductivity andspecific capacity. Silicon oxide composites with inert metal particleswith or without a pyrolytic carbon coating have shown very good cyclingperformance at high specific capacity. Suitable inert metal particlesare described further below. The milling of the silicon oxide basedmaterials with metal powders seems to reduce the introduction of inertmaterial from the grinding medium, e.g., zirconium oxide, into theproduct composite. Composites of silicon oxide, graphite, and pyrolyticcarbon in particular have shown significantly improved specific capacityand cycling performance.

HEMM and/or heat treatment under appropriate conditions can result insome disproportionation of oxygen deficient silicon oxides into SiO₂ andelemental Si. Small crystalline silicon peaks are observed under someprocessing conditions. It is possible that the processed materials havesome components of amorphous elemental silicon and/or small crystalliteswithin the structure. However, it is believed that most of the siliconoxide based materials herein have significant components of oxygendeficient silicon oxide and amounts of elemental silicon have not beenquantified. In additional embodiments, elemental silicon powders, suchas submicron silicon particles, can be included in the formation ofcomposites with silicon oxide based materials. In general, a range ofcomposites are described herein, and these can be summarized asαSiO-βGr-χHC-δM-εCNF-φSi within ranges of relative weights, as describedfurther below. As used herein, the reference to composites impliesapplication of significant combining forces, such as from HEMM milling,to intimately associate the materials, in contrast with simple blending,which is not considered to form composites.

When configured with high capacity lithium rich manganese oxides basedpositive electrodes, the silicon oxide based electrode can exhibitexcellent cycling at reasonable rates. New electrolyte with fluorinatedadditives has shown to further improve the battery performance. Highloading density electrodes with silicon oxide based active materials canbe achieved, for example, using a polyimide binder.

Lithium rich layered-layered metal oxides have been found to cycle withrelatively high specific capacities as a positive electrode activematerial. These layered-layered materials are looking very promising forcommercial applications as a new generation of high capacity positiveelectrode active material. The overall performance of the battery isbased on the capacities of both the negative and positive electrodes andtheir relative balance. An improvement in the specific capacity of thenegative electrode active material can be more significant in thecontext of overall battery design when a higher capacity positiveelectrode active material is used in the battery. Having a high capacitycathode material means that using only a fraction of the weight of ahigh capacity cathode in a battery can result in the same energy densityas a LiCoO₂ battery. Using less cathode material to obtain the sameperformance reduces the price and weight of the battery. From thisperspective, the combination of the lithium rich layered-layeredpositive electrode active material with high capacity silicon oxidebased negative electrode active material can provide particularlydesirable overall battery performance.

Supplemental lithium can replace lithium that does not cycle due to anirreversible capacity loss of the negative electrode. Furthermore, ithas been discovered that the inclusion of supplemental lithium canstabilize positive electrodes based on lithium rich layered-layeredlithium metal oxide compositions. In particular, for these lithium richmetal oxides, the supplemental lithium can stabilize the capacity of thepositive electrode compositions out to large number of cycles. Thisimprovement in cycling of the positive electrode active material isdescribed further in the copending '073 patent application.

The layered-layered lithium metal oxides, which provide a relativelylarge specific capacity, exhibit a significant irreversible capacityloss associated with changes to the material during the initial chargeof the battery. Irreversible capacity loss associated with the positiveelectrode may result in lithium that can get deposited in the negativeelectrode but which cannot be later intercalated into the positiveelectrode active material. This excess lithium from the positiveelectrode is separate from any supplemental lithium introduced into thebattery since the battery is assembled with the lithium metal oxidefully loaded with lithium pending the initial charge of the battery.

The supplemental lithium can be provided to the negative electrode invarious ways. In particular suitable approaches include, for example,introducing elemental lithium into the battery, the incorporation of asacrificial material with active lithium that can be transferred to thenegative electrode active material, or preloading of lithium into thenegative electrode active material. After the initial charge,supplemental lithium is associated with the negative electrode activematerial although a portion of the lithium can be associated withirreversible reaction byproducts, such as the solid electrolyteinterphase (SEI) layer.

The introduction of elemental lithium in association with the anode,i.e., negative electrode, can be an appropriate way to introducesupplemental lithium. In particular, elemental lithium powder or foilcan be associated with the negative electrode to supply the supplementallithium. In some embodiments, an elemental lithium powder can be placedon the surface of the electrode or on the surface of the currentcollector. A supplemental lithium source, such as elemental lithium,within the negative electrode generally may initiate reaction with thesilicon oxide based active material upon contact of the electrode withelectrolyte since the reaction is spontaneous as long as electricalconductivity is supported within the electrode structure.

In alternative or additional embodiments, a supplemental lithium sourcecan be associated with the positive electrode, i.e., cathode, or with aseparate sacrificial electrode. If a supplemental lithium source isassociated with the positive electrode or a separate sacrificialelectrode, current flows between the electrode with the supplementallithium and the negative electrode to support the respective halfreactions that ultimately results in the placement of the supplementallithium within the negative electrode active material, with possibly afraction of the supplemental lithium being consumed in side reactions,such as formation of an SEI layer or other reactions leading toirreversible capacity loss.

In further embodiments, the supplemental lithium can be placed into thenegative electrode active material prior to construction of the battery.For example, prior to assembly of the battery, supplemental lithium canbe inserted into the active material through electrochemicalintercalation/alloying. To perform the electrochemical deposition, thesilicon oxide based electrode can be assembled into a structure withelectrolyte and the supplemental lithium source, such as lithium foil.If the elemental lithium is in electrical contact with the activematerial in the presence of electrolyte, the reaction of the elementallithium with the active alloying/intercalation material can occurspontaneously. Alternatively, the structure can be assembled into a cellwith electrolyte and a separator separating the silicon oxide basedelectrode and an electrode with the supplemental lithium, such as alithium foil. Current flow through the cell can be controlled to providefor the lithium incorporation into the silicon oxide based electrode. Insuch a configuration, the silicon oxide based electrode functions as apositive electrode of a lithium cell. This cell can be cycled a fewtimes to complete any formation of an SEI layer as well as any otherinitial irreversible changes to the electrode, prior to the depositionof a desired amount of supplemental lithium into the electrode fortransfer to the ultimate battery. After deposition of a desired amountof lithium, the silicon oxide based electrode can be taken and assembledinto the ultimate lithium ion battery.

For graphitic carbon based electrodes associated with supplementallithium, the electrodes are found to have extractable lithium afteressentially fully discharging the batteries having a lithium metal oxidepositive electrode active material after cycling for relatively largenumbers of cycles. The lithium is supplied in the batteries from thepositive electrode active material as well as the supplemental lithium.This residual lithium is found to stabilize the battery cycling whenused with lithium rich positive electrode active materials. Also, theamount of residual lithium is found to gradually diminish with largernumbers of cycles. See the '073 patent application referenced above.Based on the measurements for the graphitic carbon electrodes, it isanticipated that the silicon oxide based electrodes with supplementallithium can similarly exhibit residual lithium that can be extractedfrom the electrodes after discharging the battery with a lithium metaloxide positive electrode.

Silicon oxide has attracted significant amount of attention as apotential negative electrode material due to its high specific capacitywith respect to intake and release of lithium and promising cyclingproperties. See, for example, published U.S. patent application2004/0033419 to Funabiki, entitled “Negative Electrode Active Material,Negative Electrode Using the Same, Non-Aqueous Electrolyte Battery Usingthe Same, and Method for Preparing the Same,” incorporated herein byreference. It was further recognized that association of conductivecarbon with the silicon oxide active material can improve theperformance of the silicon oxide material in a lithium ion battery.Composites with electrically conductive materials and silicon oxideactive material described herein provide very good cycling performance.

As described herein, high energy milling is used to fracture siliconoxide particles to a smaller size. The results herein suggest that thesmaller particles can cycle significantly better, perhaps due to theability of the smaller particles to accommodate volume changes of theparticles over cycling of the materials. The milling process canincorporate electrically conductive diluents to form an intimatecomposite through the milling process. Graphitic carbon, e.g.,nanostructured conductive carbon, can provide a good electricallyconductive medium for the formation of composites with silicon oxide.Furthermore, it has been found that metal particles provide desirablemilling properties as well as a suitable electrically conductive diluentfor the formation of corresponding composites. In particular, it hasbeen found that milling with metal powders can provide for the use ofdesirable milling conditions while obtaining reduced amounts of millingmedia within the product composite. High energy milling can generally beperformed with a hard ceramic milling media, such as zirconium oxideparticles. Milling can result in the incorporation of some milling mediainto the product composite material. Since the milling media iselectrically insulating and electrochemically inert, it is desirable tokeep the amount of milling media in the product composite material,after separation of the bulk quantities of milling beads, to a low orpossibly undetectable level.

The objective for the design of improved silicon oxide based materialsis to further stabilize the negative electrode materials over cyclingwhile maintaining a high specific capacity. Thus, high energy millingcan be performed to form composites with electrically conductivematerials. As described herein, pyrolytic carbon coatings are alsoobserved to stabilize silicon oxide based materials with respect tobattery performance. In particular, the pyrolytic carbon coatings can beplaced over the initially prepared composites to provide an additionalelectrically conductive component of the product material. Thecombination of the pyrolytic carbon with a silicon oxide-particulateconductor composite provides surprisingly improved performance in someembodiments.

With respect to the composite materials, silicon oxide components can becombined with, for example, carbon nanoparticles and/or carbonnanofibers. The components can be, for example, milled to form thecomposite, in which the materials are intimately associated. Generally,it is believed that the association has a mechanical characteristic,such as the carbon coated over or mechanically affixed with the siliconoxide materials. In additional or alternative embodiments, the siliconoxide can be milled with metal powders, in which the silicon oxide ismilled to a smaller particle size and the metal is intimately combinedwith the silicon oxide material to form a composite material, forexample with a nanostructure. The carbon components can be combined withthe silicon-metal alloys to form multi-component composites. Thecomposite materials with intimately combined components aredistinguishable from simple blends of components held together with apolymer binder, which lacks mechanical and/or chemical interactions toform a single composite material.

Desirable carbon coatings can be formed by pyrolizing organiccompositions. The organic compositions can be pyrolyzed at relativelyhigh temperatures, e.g., about 800° C. to about 900° C., to form a hardamorphous coating. In some embodiments, the desired organic compositionscan be dissolved in a suitable solvent, such as water and/or volatileorganic solvents for combining with the silicon oxide based component.The dispersion can be well mixed with silicon oxide based composition.After drying the mixture to remove the solvent, the dried mixture can beheated in an oxygen free atmosphere to pyrolyze the organic composition,such as organic polymers, some lower molecular solid organiccompositions and the like, and to form a carbon coating. The carboncoating can lead to surprisingly significant improvement in the capacityof the resulting material. Also, environmentally friendly organiccompositions, such as sugars and citric acid, can be used as desirableprecursors for the formation of pyrolytic carbon coatings. In someembodiments, organic polymers can be blended with the silicon oxidebased materials for thermal processing to form pyrolytic carbon. Infurther embodiments, elemental metal coatings, such as silver or copper,can be applied as an alternative to a pyrolytic carbon coating toprovide electrical conductivity and to stabilize silicon oxide basedactive material. The elemental metal coatings can be applied throughsolution based reduction of a metal salt.

The silicon oxide based materials can be incorporated into suitableelectrode structures generally with a suitable polymer binder andoptionally mixed with electrically conductive powders. It has been foundthat polyimide binders are particularly desirable for silicon oxidebased materials. The high capacity silicon oxide based materials are ofparticular value in combination with a high capacity positive electrodeactive material. Traditionally, the anode and cathode are relativelybalanced so that the battery does not involve significant waste withassociated cost of unused electrode capacity as well as for theavoidance of corresponding weight and volume associated with unusedelectrode capacity. With the materials described herein, it can bepossible to get high capacity results simultaneously for both electrodesin the lithium ion battery. Furthermore, cycling capacity of bothelectrodes can independently fade, and the capacities of both electrodesare subject to irreversible capacity loss, and approaches to addressboth of these issues are described herein. The positive electrodes withlithium rich layered-layered compositions can exhibit a significantfirst cycle irreversible capacity loss. However, high capacity siliconoxide based anodes can generally exhibit contributions to IRCLsignificantly greater than the positive electrode active material.

The positive electrode active material can be designed to reduce IRCLassociated with the positive electrode, such as with a coating appliedto the positive electrode active material. Furthermore, supplementallithium can be used as a substitute for additional capacity of thepositive electrode to compensate for the relatively large IRCL of thenegative electrode. The supplemental lithium can compensate for thelarge IRCL of the negative electrode. Thus, if the supplemental lithiumis selected to appropriately compensate for the negative electrode IRCL,the remaining observed IRCL can be attributed to the positive electrodeactive material. With appropriate stabilization of the negativeelectrode and positive electrode, a battery with high capacity materialsin both electrodes can exhibit high specific capacities for bothelectrodes over at least a moderate number of cycles.

To achieve cycling of the battery without lithium plating, the negativeelectrode generally is balanced to at least about 100% of the positiveelectrode capacity. The electrode capacities are evaluated independentlyagainst a lithium metal electrode, as described further below. On theother hand, for embodiments with supplemental lithium, the supplementallithium can be designed to compensate for the IRCL such that the cyclingcapacities of the negatives electrode and positive electrode can beroughly balanced or with some excess negative electrode capacity,although a greater amount of supplemental lithium can be used ifdesired.

Improved performance of silicon oxide based batteries is also observedwith the addition of a halogenated carbonates as an additive to theelectrolyte. For example, fluoroethylene carbonate (FEC) has beenproposed to improve the safety of batteries due to its nonflammability,to expand the operating cell voltage due to its high oxidationresistance, to improve cycle performance by forming an electrochemicallystable SEI that included LiF and silicon (Si) fluorides on a Si-basedanode, and many other advantages [1-6]. 1. R. McMillan, H. Slegr, Z. X.Shu, and W. Wang, J. Power Sources, 81, 20 (1999). 2. N.-S. Choi, K. H.Yew, K. Y. Lee, M. Sung, H. Kim, and S.-S. Kim, J. Power Sources, 161,1254 (2006). 3. I. A. Profatilova, S.-S. Kim, and N.-S. Choi,Electrochim. Acta, 54, 4445 (2009). 4. T. Achiha, T. Nakajima, Y.Ohzawa, M. Koh, A. Yamauchi, M. Kagawa, and H. Aoyama, J. Electrochem.Soc., 156, A483 (2009). 5. J. Yamaki, S. Yamami, T. Doi, and S. Okada,Electrochem. Soc., 602, 263 (2006). 6. K. Naoi, E. Iwama, N. Ogihara, Y.Nakamura, H. Segawa, and Y. Ino, J. Electrochem. Soc., 156, A272 (2009).A halogenated carbonate additive has been found to provide surprisinglysignificant improvement in the performance of the batteries based onsilicon oxide active materials.

Lithium Ion Battery Structure

Lithium ion batteries generally comprise a positive electrode (cathode),a negative electrode (anode), a separator between the negative electrodeand the positive electrode and an electrolyte comprising lithium ions.The electrodes are generally associated with metal current collectors,such as metal foils. Lithium ion batteries refer to batteries in whichthe negative electrode active material is a material that takes uplithium during charging and releases lithium during discharging.Referring to FIG. 1, a battery 100 is shown schematically having anegative electrode 102, a positive electrode 104, and a separator 106between negative electrode 102 and positive electrode 104. A battery cancomprise multiple positive electrodes and multiple negative electrodes,such as in a stack, with appropriately placed separators. Electrolyte incontact with the electrodes provides ionic conductivity through theseparator between electrodes of opposite polarity. A battery generallycomprises current collectors 108, 110 associated respectively withnegative electrode 102 and positive electrode 104. The basic batterystructures and compositions are described in this section andmodifications related to incorporation of supplemental lithium aredescribed further below.

The nature of the positive electrode active material and the negativeelectrode active material influences the resulting voltage of thebattery since the voltage is the difference between the half cellpotentials at the cathode and anode. Suitable positive electrode activematerials are described below, and the materials of particular interestare lithium metal oxides. In general, suitable negative electrodelithium intercalation/alloying compositions can include, for example,graphite, synthetic graphite, coke, fullerenes, other graphitic carbons,niobium pentoxide, tin alloys, silicon, silicon oxide, silicon alloys,silicon-based composites, titanium oxide, tin oxide, and lithiumtitanium oxide, such as Li_(x)TiO₂, 0.5<x≦1 or Li_(1+x)Ti_(2−x)O₄,0≦x≦⅓. Graphitic carbon and metal oxide negative electrode compositionstake up and release lithium through an intercalation or similar process.Silicon and tin alloys form alloys with the lithium metal to take uplithium and release lithium from the alloy to correspondingly releaselithium. Negative electrode active materials of particular interestherein are silicon oxide based materials described in detail below. Ingeneral, if the battery does not include supplemental lithium, thepositive electrode and negative electrode are balanced such that thecapacities of the negative electrode active material is from about 100to about 110 percent of the capacity of the positive electrode activematerial. The positive electrode active material capacity can beestimated from the theoretical capacity of the material, and thenegative electrode capacity can be measured by cycling the materialagainst lithium metal foil. The balancing of the battery whensupplemental lithium is present is described further below.

The positive electrode active compositions and negative electrode activecompositions generally are powder compositions that are held together inthe corresponding electrode with a polymer binder. The binder providesionic conductivity to the active particles when in contact with theelectrolyte. Suitable polymer binders include, for example sodiumcarboxy methyl cellulose (CMC), polyvinylidine fluoride (PVDF),polyimide, polyethylene oxide, polyethylene, polypropylene,polytetrafluoroethylene, polyacrylates, rubbers, e.g.ethylene-propylene-diene monomer (EPDM) rubber or styrene butadienerubber (SBR), copolymers thereof, or mixtures thereof. In particular,thermally curable polyimide polymers have been found desirable, whichmay be due to their high mechanical strength. Table I provides suppliersof polyimide polymers, and names of corresponding polyimide polymers.

TABLE I Supplier Binder New Japan Chemical Co., Ltd. Rikacoat PN-20Rikacoat EN-20 Rikacoat SN-20 HD MicroSystems PI-2525 PI-2555 PI-2556PI-2574 AZ Electronic Materials PBI MRS0810H Ube Industries. Ltd.U-Varnish S U-Varnish A Maruzen Petrochemical Co., Ltd. Bani-X(Bis-allyl-nadi-imide) Toyobo Co., Ltd. Vyromax HR16NN

With respect to polymer properties, some significant properties forelectrode application are summarized in Table II.

TABLE II Tensile Elastic Elongation Strength Modulus Viscosity Binder(%) (MPa) (psi) (P) PVDF  5-20 31-43 160000 10-40 Polyimide  70-100150-300 40-60 CMC 30-40 10-15 30

The elongation refers to the percent elongation prior to tearing of thepolymer. In general, to accommodate the silicon oxide based materials,it is desirable to have an elongation of at least about 50% and infurther embodiments at least about 70%. Similarly, it is desirable forthe polymer binder to have a tensile strength of at least about 100 MPaand in further embodiments at least about 150 MPa. Tensile strengths canbe measured according to procedures in ASTM D638-10 Standard Test Methodfor Tensile Properties of Plastics, incorporated herein by reference. Aperson of ordinary skill in the art will recognize that additionalranges of polymer properties within the explicit ranges above arecontemplated and are within the present disclosure. The particle loadingin the binder can be large, such as greater than about 80 weight percentup to about 97 percent or more. To form the electrode, the powders canbe blended with the polymer in a suitable liquid, such as a solvent forthe polymer. The resulting paste can be pressed into the electrodestructure.

The positive electrode composition, and possibly the negative electrodecomposition, generally also comprises an electrically conductive powderdistinct from the electroactive composition. Suitable supplementalelectrically conductive powders include, for example, graphite, carbonblack, metal powders, such as silver powders, metal fibers, such asstainless steel fibers, and the like, and combinations thereof.Generally, a positive electrode can comprise from about 1 weight percentto about 25 weight percent, and in further embodiments from about 2weight percent to about 15 weight percent distinct electricallyconductive powder. While the negative electrode can comprise anelectrically conductive material incorporated into the composite, thenegative electrode can further comprise an electrically conductivematerial that is simply blended into the blend with the polymer suchthat the additional conductor is not intimately combined with thesilicon oxide. With respect to the blended electrically conductivecompositions, the negative electrode can comprise from about 1 weightpercent to about 30 weight percent additional conductor and in furtherembodiments from about 2 weight percent to about 15 weight percentadditional electrical conductor. A person of ordinary skill in the artwill recognize that additional ranges of amounts of electricallyconductive powders and polymer binders within the explicit ranges aboveare contemplated and are within the present disclosure.

The electrode generally is associated with an electrically conductivecurrent collector to facilitate the flow of electrons between theelectrode and an exterior circuit. The current collector can comprisemetal, such as a metal foil or a metal grid. In some embodiments, thecurrent collector can be formed from nickel, aluminum, stainless steel,copper or the like. The electrode material can be cast as a thin filmonto the current collector. The electrode material with the currentcollector can then be dried, for example in an oven, to remove solventfrom the electrode. In some embodiments, the dried electrode material incontact with the current collector foil or other structure can besubjected to a pressure, such as, from about 2 to about 10 kg/cm²(kilograms per square centimeter).

The separator is located between the positive electrode and the negativeelectrode. The separator is electrically insulating while providing forat least selected ion conduction between the two electrodes. A varietyof materials can be used as separators. Commercial separator materialsare generally formed from polymers, such as polyethylene and/orpolypropylene that are porous sheets that provide for ionic conduction.Commercial polymer separators include, for example, the Celgard® line ofseparator material from Hoechst Celanese, Charlotte, N.C. Also,ceramic-polymer composite materials have been developed for separatorapplications. These composite separators can be stable at highertemperatures, and the composite materials can significantly reduce thefire risk. The polymer-ceramic composites for separator materials aredescribed further in U.S. patent application 2005/0031942A to Hennige etal., entitled “Electric Separator, Method for Producing the Same and theUse Thereof,” incorporated herein by reference. Polymer-ceramiccomposites for lithium ion battery separators are sold under thetrademark Separion® by Evonik Industries, Germany.

We refer to solutions comprising solvated ions as electrolytes, andionic compositions that dissolve to form solvated ions in appropriateliquids are referred to as electrolyte salts. Electrolytes for lithiumion batteries can comprise one or more selected lithium salts.Appropriate lithium salts generally have inert anions. Suitable lithiumsalts include, for example, lithium hexafluorophosphate, lithiumhexafluoroarsenate, lithium bis(trifluoromethyl sulfonyl imide), lithiumtrifluoromethane sulfonate, lithium tris(trifluoromethyl sulfonyl)methide, lithium tetrafluoroborate, lithium perchlorate, lithiumtetrachloroaluminate, lithium chloride, lithium difluoro oxalato borate,and combinations thereof. Traditionally, the electrolyte comprises a 1 Mconcentration of the lithium salts, although greater or lesserconcentrations can be used. Particularly useful electrolytes for highvoltage lithium-ion batteries are described further in copending U.S.patent application Ser. No. 12/630,992 filed on Dec. 4, 2009 now U.S.Pat. No. 8,993,177 to Amiruddin et al. (the '992 application), entitled“Lithium Ion Battery With High Voltage Electrolytes and Additives,”incorporated herein by reference.

For lithium ion batteries of interest, a non-aqueous liquid is generallyused to dissolve the lithium salt(s). The solvent generally does notdissolve the electroactive materials. Appropriate solvents include, forexample, propylene carbonate, dimethyl carbonate, diethyl carbonate,2-methyl tetrahydrofuran, dioxolane, tetrahydrofuran, methyl ethylcarbonate, γ-butyrolactone, dimethyl sulfoxide, acetonitrile, formamide,dimethyl formamide, triglyme (tri(ethylene glycol) dimethyl ether),diglyme (diethylene glycol dimethyl ether), DME (glyme or1,2-dimethyloxyethane or ethylene glycol dimethyl ether), nitromethaneand mixtures thereof. Particularly useful solvents for high voltagelithium-ion batteries are described further in the copending '992application.

Additives to the electrolytes can further provide performanceimprovements. In particular, the performance of silicon oxide basedbatteries can have significant performance improvements with theaddition of halogenated carbonates to the electrolyte. Suitablehalogenated carbonates include, for example, fluoroethylene carbonate(C₃H₃FO₃), fluorinated vinyl carbonate, monochloro ethylene carbonate,monobromo ethylene carbonate,4-(2,2,3,3-tetrafluoropropoxymethyl)-[1,3]dioxolan-2-one,4-(2,3,3,3-tetrafluoro-2-trifluoro methyl-propyl)-[1,3]dioxolan-2-one,4-trifluoromethyl-1,3-dioxolan-2-one, bis(2,2,3,3-tetrafluoro-propyl)carbonate, bis(2,2,3,3,3-pentafluoro-propyl) carbonate, mixtures thereofand the like. Note that ethylene carbonate is also known by its IUPACname of 1,3-dioxolan-2-one. In general, the electrolyte can comprisefrom about 1 volume percent to about 35 volume percent halogenatedcarbonate, in further embodiments from about 2 volume percent to about30 volume percent and in other embodiments from about 3 volume percentto about 25 volume percent halogenated carbonate in the electrolyte. Aperson of ordinary skill in the art will recognize that additionalranges of halogenated carbonate concentrations within the explicitranges above are contemplated and are within the present disclosure. Asdescribed further in the Examples below, the incorporation ofhalogenated carbonate into the electrolyte has been observed tosignificantly improve the specific capacity and the cycling propertiesof batteries incorporating silicon oxide active materials.

The electrodes described herein can be incorporated into variouscommercial battery designs, such as prismatic shaped batteries, woundcylindrical batteries, coin batteries or other reasonable batteryshapes. The batteries can comprise a single electrode stack or aplurality of electrodes of each charge assembled in parallel and/orseries electrical connection(s). Appropriate electrically conductivetabs can be welded or the like to the current collectors, and theresulting jellyroll or stack structure can be placed into a metalcanister or polymer package, with the negative tab and positive tabwelded to appropriate external contacts. Electrolyte is added to thecanister, and the canister is sealed to complete the battery. Somepresently used rechargeable commercial batteries include, for example,the cylindrical 18650 batteries (18 mm in diameter and 65 mm long) and26700 batteries (26 mm in diameter and 70 mm long), although otherbattery sizes can be used. Pouch batteries can be constructed asdescribed in published U.S. patent application 2009/0263707 to Buckleyet al, entitled “High Energy Lithium Ion Secondary Batteries”,incorporated herein by reference.

Positive Electrode Active Compositions

In general, the lithium ion battery positive electrode materials can beany reasonable positive electrode active material, such asstoichiometric layered cathode materials with hexagonal latticestructures, such as LiCoO₂, LiNiO₂, LiMnO₂, Li(CoNiMn)_(1/3)O₂,Li(CoNiMnAl)_(1/4)O₂ or the like; cubic spinel cathode materials such asLiMn₂O₄, LiNi_(0.5)Mn_(1.5)O₄, Li₄Mn₅O₁₂, or the like; olivine LiMPO₄(M=Fe, Co, Mn, combinations thereof and the like) type materials;layered cathode materials such as Li_(1+x)(NiCoMn)_(0.33−x)O₂ (0≦x<0.3)systems; layer-layer composites, such as xLi₂MnO₃.(1−x)LiMO₂ where M canbe Ni, Co, Mn, combinations thereof and the like; and compositestructures like layered-spinel structures such as LiMn₂O₄.LiMO₂. Inadditional or alternative embodiments, a lithium rich composition can bereferenced relative to a composition LiMO₂, where M is one or moremetals with an average oxidation state of +3. Generally, the lithiumrich compositions can be represented approximately with a formulaLi_(1+x)M_(1−y)O_(2−z)F_(z) where M is one or more metal elements, x isfrom about 0.01 to about 0.33, y is from about x−0.2 to about x+0.2 withthe proviso that y≧0, and z is from 0 to about 0.2. In thelayered-layered composite compositions, x is approximately equal to y.In general, the additional lithium in the lithium rich compositions isaccessed at higher voltages such that the initial charge takes place ata relatively higher voltage to access the additional capacity.

Lithium rich positive electrode active materials of particular interestcan be represented approximately by a formulaLi_(1+b)Ni_(α)Mn_(β)Co_(γ)A_(δ)O_(2−z)F_(z), where b ranges from about0.01 to about 0.3, α ranges from about 0 to about 0.4, β range fromabout 0.2 to about 0.65, γ ranges from 0 to about 0.46, δ ranges from 0to about 0.15 and z ranges from 0 to about 0.2 with the proviso thatboth α and γ are not zero, and where A is Mg, Sr, Ba, Cd, Zn, Al, Ga, B,Zr, Ti, Ca, Ce, Y, Nb, Cr, Fe, V, Li or combinations thereof. A personof ordinary skill in the art will recognize that additional ranges ofparameter values within the explicit compositional ranges above arecontemplated and are within the present disclosure. To simplify thefollowing discussion in this section, the optional fluorine dopant isnot discussed further. Desirable lithium rich compositions with afluorine dopant are described further in published U.S. patentapplication 2010/0086854 to Kumar et al., entitled “Fluorine DopedLithium Rich Metal Oxide Positive Electrode Battery Materials With HighSpecific Capacity and Corresponding Batteries,” incorporated herein byreference. Compositions in which A is lithium as a dopant forsubstitution for Mn are described in published U.S. patent application2011/0052989 to Venkatachalam et al., entitled “Lithium Doped CathodeMaterial,” incorporated herein by reference. The specific performanceproperties obtained with +2 metal cation dopants, such as Mg⁺², aredescribed in copending U.S. patent application Ser. No. 12/753,312 nowU.S. Pat. No. 8,741,484 to Karthikeyan et al., entitled “Doped PositiveElectrode Active Materials and Lithium Ion Secondary BatteriesConstructed Therefrom,” incorporated herein by reference.

If b+α-β+γ+δ approximately equals to 1, the positive electrode materialwith the formula above can be represented approximately in two componentnotation as x Li₂M′O₃.(1−x)LiMO₂ where 0<x<1, M is one or more metalcations with an average valance of +3 within some embodiments at leastone cation being a Mn ion or a Ni ion and where M′ is one or more metalcations with an average valance of +4 such as Mn⁺⁴. It is believed thatthe layered-layered composite crystal structure has a structure with theexcess lithium supporting the stability of the material. For example, insome embodiments of lithium rich materials, a Li₂MnO₃ material may bestructurally integrated with a layered LiMO₂ component where Mrepresents selected non-lithium metal elements or combinations thereof.These compositions are described generally, for example, in U.S. Pat.No. 6,680,143 to Thackeray et al., entitled “Lithium Metal OxideElectrodes for Lithium Cells and Batteries,” incorporated herein byreference.

Recently, it has been found that the performance properties of thepositive electrode active materials can be engineered around thespecific design of the composition stoichiometry. The positive electrodeactive materials of particular interest can be represented approximatelyin two component notation as x Li₂MnO₃.(1−x) LiMO₂, where M is one ormore metal elements with an average valance of +3 and with one of themetal elements being Mn and with another metal element being Ni and/orCo. In general, 0<x<1, but in some embodiments 0.03≦x≦0.55, in furtherembodiments 0.075≦x≦0.50, in additional embodiments 0.1≦x≦0.45, and inother embodiments 0.15≦x≦0.425. A person of ordinary skill in the artwill recognize that additional ranges within the explicit ranges ofparameter x above are contemplated and are within the presentdisclosure. For example, M can be a combination of nickel, cobalt andmanganese, which, for example, can be in oxidation states Ni⁺², Co⁺³,and Mn⁺⁴ within the initial lithium manganese oxides. The overallformula for these compositions can be written asLi_(2(i+x)/(2+x))Mn_(2x/(2+x))M_((2−2x)/(2+x))O₂. In the overallformula, the total amount of manganese has contributions from bothconstituents listed in the two component notation. Thus, in some sensethe compositions are manganese rich.

In some embodiments, M can be written as Ni_(u)Mn_(v)Co_(w)A_(y). Forembodiments in which y=0, this simplifies to Ni_(u)Mn_(v)Co_(w). If Mincludes Ni, Co, Mn, and optionally A the composition can be writtenalternatively in two component notation and single component notation asthe following.

xLi₂MnO₃·(1−x)LiNi_(u)Mn_(v)Co_(w)A_(y)O₂,  (1)

Li_(1+b)Ni_(α)Mn_(β)Co_(γ)A_(δ)O₂,  (2)

with u+v+w+y≈1 and b+a+β+γ+δ≈1. The reconciliation of these two formulasleads to the following relationships:

b=x/(2+x),

α=2u(1−x)/(2+x),

β=2x/(2+x)+2v(1−x)/(2+x),

γ=2w(1−x)/(2+x),

δ=2y(1−x)/(2+x),

and similarly,

x=2b/(1−b),

u=α/(1−3b),

v=((β−2b)/(1−3b),

w=γ/(1−3b),

y=δ/(1−3b).

In some embodiments, it may be desirable to have u≈v, such thatLiNi_(u)Mn_(v)Co_(w)A_(y)O₂ becomes approximatelyLiNi_(u)Mn_(u)Co_(w)A_(y)O₂. In this composition, when y=0, the averagevalance of Ni, Co and Mn is +3, and if u≈v, then these elements can havevalances of approximately Ni⁺², Co⁺³ and Mn⁺⁴ to achieve the averagevalance. When the lithium is hypothetically fully extracted, all of theelements go to a +4 valance. A balance of Ni and Mn can provide for Mnto remain in a +4 valance as the material is cycled in the battery. Thisbalance avoids the formation of Mn⁺³, which has been associated withdissolution of Mn into the electrolyte and a corresponding loss ofcapacity.

In further embodiments, the composition can be varied around the formulaabove such that LiNi_(u+Δ)Mn_(u−Δ)Co_(w)A_(y)O₂, where the absolutevalue of Δ generally is no more than about 0.3 (i.e., −0.3≦Δ≦0.3), inadditional embodiments no more than about 0.2 (−0.2≦Δ≦0.2) in someembodiments no more than about 0.175 (−0.175≦Δ≦0.175) and in furtherembodiments no more than about 0.15 (−0.15≦Δ≦0.15). Desirable ranges forx are given above. With 2u+w+y≈1, desirable ranges of parameters are insome embodiments 0≦w≦1, 0≦u≦0.5, 0≦y≦0.1 (with the proviso that both u+Aand w are not zero), in further embodiments, 0.1≦w≦0.6, 0.1≦u≦0.45,0≦y≦0.075, and in additional embodiments 0.2≦w≦0.5, 0.2≦u≦0.4, 0≦y≦0.05.A person of ordinary skill in the art will recognize that additionalranges of composition parameters within the explicit ranges above arecontemplated and are within the present disclosure. As used herein, thenotation (value1≦variable≦value2) implicitly assumes that value 1 andvalue 2 are approximate quantities. The engineering of the compositionto obtain desired battery performance properties is described further inpublished U.S. patent application number 2011/0052981 to Lopez et al.,entitled “Layer-Layer Lithium Rich Complex Metal Oxides With HighSpecific Capacity and Excellent Cycling,” incorporated herein byreference.

The formulas presented herein for the positive electrode activematerials are based on the molar quantities of starting materials in thesynthesis, which can be accurately determined. With respect to themultiple metal cations, these are generally believed to bequantitatively incorporated into the final material with no knownsignificant pathway resulting in the loss of the metals from the productcompositions. Of course, many of the metals have multiple oxidationstates, which are related to their activity with respect to thebatteries. Due to the presence of the multiple oxidation states andmultiple metals, the precise stoichiometry with respect to oxygengenerally is only roughly estimated based on the crystal structure,electrochemical performance and proportions of reactant metals, as isconventional in the art. However, based on the crystal structure, theoverall stoichiometry with respect to the oxygen is reasonablyestimated. All of the protocols discussed in this paragraph and relatedissues herein are routine in the art and are the long establishedapproaches with respect to these issues in the field.

A co-precipitation process has been performed for the desired lithiumrich metal oxide materials described herein having nickel, cobalt,manganese and additional optional metal cations in the composition andexhibiting the high specific capacity performance. In addition to thehigh specific capacity, the materials can exhibit a good tap densitywhich leads to high overall capacity of the material in fixed volumeapplications. Specifically, lithium rich metal oxide compositions formedby the co-precipitation process were used in coated forms to generatethe results in the Examples below.

Specifically, the synthesis methods based on co-precipitation have beenadapted for the synthesis of compositions with the formulaLi_(1+b)Ni_(α)Mn_(β)Co_(γ)A_(δ)O_(2−z)F_(z), as described above. In theco-precipitation process, metal salts are dissolved into an aqueoussolvent, such as purified water, with a desired molar ratio. Suitablemetal salts include, for example, metal acetates, metal sulfates, metalnitrates, and combination thereof. The concentration of the solution isgenerally selected between 1M and 3M. The relative molar quantities ofmetal salts can be selected based on the desired formula for the productmaterials. Similarly, the dopant elements can be introduced along withthe other metal salts at the appropriate molar quantity such that thedopant is incorporated into the precipitated material. The pH of thesolution can then be adjusted, such as with the addition of Na₂CO₃and/or ammonium hydroxide, to precipitate a metal hydroxide or carbonatewith the desired amounts of metal elements. Generally, the pH can beadjusted to a value between about 6.0 to about 12.0. The solution can beheated and stirred to facilitate the precipitation of the hydroxide orcarbonate. The precipitated metal hydroxide or carbonate can then beseparated from the solution, washed and dried to form a powder prior tofurther processing. For example, drying can be performed in an oven atabout 110° C. for about 4 to about 12 hours. A person of ordinary skillin the art will recognize that additional ranges of process parameterswithin the explicit ranges above are contemplated and are within thepresent disclosure.

The collected metal hydroxide or carbonate powder can then be subjectedto a heat treatment to convert the hydroxide or carbonate composition tothe corresponding oxide composition with the elimination of water orcarbon dioxide. Generally, the heat treatment can be performed in anoven, furnace or the like. The heat treatment can be performed in aninert atmosphere or an atmosphere with oxygen present. In someembodiments, the material can be heated to a temperature of at leastabout 350° C. and in some embodiments from about 400° C. to about 800°C. to convert the hydroxide or carbonate to an oxide. The heat treatmentgenerally can be performed for at least about 15 minutes, in furtherembodiments from about 30 minutes to 24 hours or longer, and inadditional embodiments from about 45 minutes to about 15 hours. Afurther heat treatment can be performed at a second higher temperatureto improve the crystallinity of the product material. This calcinationstep for forming the crystalline product generally is performed attemperatures of at least about 650° C., and in some embodiments fromabout 700° C. to about 1200° C., and in further embodiments from about700° C. to about 1100° C. The calcination step to improve the structuralproperties of the powder generally can be performed for at least about15 minutes, in further embodiments from about 20 minutes to about 30hours or longer, and in other embodiments from about 1 hour to about 36hours. The heating steps can be combined, if desired, with appropriateramping of the temperature to yield desired materials. A person ofordinary skill in the art will recognize that additional ranges oftemperatures and times within the explicit ranges above are contemplatedand are within the present disclosure.

The lithium element can be incorporated into the material at one or moreselected steps in the process. For example, a lithium salt can beincorporated into the solution prior to or upon performing theprecipitation step through the addition of a hydrated lithium salt. Inthis approach, the lithium species is incorporated into the hydroxide orcarbonate material in the same way as the other metals. Also, due to theproperties of lithium, the lithium element can be incorporated into thematerial in a solid state reaction without adversely affecting theresulting properties of the product composition. Thus, for example, anappropriate amount of lithium source generally as a powder, such asLiOH.H₂O, LiOH, Li₂CO₃, or a combination thereof, can be mixed with theprecipitated metal carbonate or metal hydroxide. The powder mixture isthen advanced through the heating step(s) to form the oxide and then thecrystalline final product material.

Further details of the hydroxide co-precipitation process are describedin published U.S. patent application 2010/0086853A to Venkatachalam etal. entitled “Positive Electrode Material for Lithium Ion BatteriesHaving a High Specific Discharge Capacity and Processes for theSynthesis of these Materials”, incorporated herein by reference. Furtherdetails of the carbonate co-precipitation process are described inpublished U.S. patent application 2010/0151332A to Lopez et al. entitled“Positive Electrode Materials for High Discharge Capacity Lithium IonBatteries,” incorporated herein by reference.

Also, it has been found that coating the positive electrode activematerials can improve the cycling of lithium-based batteries. Thecoating can also be effective at reducing the irreversible capacity lossof the battery as well as increasing the specific capacity generally.The amount of coating material can be selected to accentuate theobserved performance improvements. Suitable coating materials, which aregenerally believed to be electrochemically inert during battery cycling,can comprise metal fluorides, metal oxides, metal non-fluoride halidesor metal phosphates. The results in the Examples below are obtained withmaterials coated with metal fluorides.

For example, the general use of metal fluoride compositions as coatingsfor cathode active materials, specifically LiCoO₂ and LiMn₂O₄, isdescribed in published PCT application WO 2006/109930A to Sun et al.,entitled “Cathode Active Material Coated with Fluorine Compound forLithium Secondary Batteries and Method for Preparing the Same,”incorporated herein by reference. Improved metal fluoride coatings withappropriately engineered thicknesses are described in published U.S.patent application number 2011/0111298 to Lopez et al, (the '298application) entitled “Coated Positive Electrode Materials for LithiumIon Batteries,” incorporated herein by reference. Suitable metal oxidecoatings are described further, for example, in published U.S. patentapplication number 2011/0076556 to Karthikeyan et al. entitled “MetalOxide Coated Positive Electrode Materials for Lithium-Based Batteries”,incorporated herein by reference. The discovery of non-fluoride metalhalides as desirable coatings for cathode active materials is describedin copending U.S. patent application Ser. No. 12/888,131 now U.S. Pat.No. 8,663,849 to Venkatachalam et al., entitled “Metal Halide Coatingson Lithium Ion Battery Positive Electrode Materials and CorrespondingBatteries,” incorporated herein by reference. In general, the coatingscan have an average thickness of no more than 25 nm, in some embodimentsfrom about 0.5 nm to about 20 nm, in other embodiments from about 1 nmto about 12 nm, in further embodiments from 1.25 nm to about 10 nm andin additional embodiments from about 1.5 nm to about 8 nm. A person ofordinary skill in the art will recognize that additional ranges ofcoating material within the explicit ranges above are contemplated andare within the present disclosure.

A metal fluoride coating can be deposited using a solution basedprecipitation approach. A soluble composition of the desired metal canbe dissolved in a suitable solvent, such as an aqueous solvent. Then,NH₄F can be gradually added to the dispersion/solution to precipitatethe metal fluoride. The total amount of coating reactants can beselected to form the desired thickness of coating, and the ratio ofcoating reactants can be based on the stoichiometry of the coatingmaterial. After removing the coated electroactive material from thesolution, the material can be dried and heated, generally above about250° C., to complete the formation of the coated material. The heatingcan be performed under a nitrogen atmosphere or other substantiallyoxygen free atmosphere.

An oxide coating is generally formed through the deposition of aprecursor coating onto the powder of active material. The precursorcoating is then heated to form the metal oxide coating. Suitableprecursor coating can comprise corresponding metal hydroxides, metalcarbonates or metal nitrates. The metal hydroxides and metal carbonateprecursor coating can be deposited through a precipitation process sincethe addition of ammonium hydroxide and/or ammonium carbonate can be usedto precipitate the corresponding precursor coatings. The precursorcoating can be heated, generally above about 250° C., to decompose theprecursor to form the oxide coating.

Negative Electrode Active Materials

Desirable high capacity negative electrode active materials can comprisesilicon oxide based materials, such as composites with nanostructuredcarbon materials or metal powders. In general, the silicon oxidematerials have been found to have significantly improved performance ifthey are milled to a small particle size, whether or not formed into acomposite. In particular, active silicon oxide based material cancomprise oxygen deficient silicon oxide, i.e., that the material has aformula SiO_(x) where x<2. The oxygen deficient silicon oxide can takeup and release lithium with a large specific capacity and as describedherein this material can be incorporated into lithium ion batteries withgood cycling properties. Oxygen deficient silicon oxide can be unstablewith respect to a disproportionation reaction to form elemental siliconand silicon dioxide, although this reaction does not seem to take placewithout the application of heat or with significant milling times. Theprocessing to form desired forms of silicon oxide based materials canresult in some formation of elemental silicon, which is electroactive,and silicon dioxide, which is believed to be inert in a lithium ionbattery. The structure of the oxygen deficient silicon oxide has beendebated, and evidence suggests the formation of amorphous domains ofelemental silicon surrounded by amorphous domains of silicon dioxide,but the particular microscopic structure of the oxygen deficient siliconoxide material is not particularly relevant for the present discussion.In general, processing is performed under conditions in which only smallamounts of crystalline silicon is observed in x-ray diffractograms, suchthat it is believed that a significant majority of the material remainsas an active silicon oxide that is oxygen deficient relative to SiO₂. Ingeneral, it is desirable to mill the material to form smaller particlesof the silicon oxide based material, and in some embodiments it may bedesirable to form a composite with an electrically conductive component.

Suitable composites as described herein can comprise silicon oxide,carbon components, such as graphitic particles (Gr), inert metal powders(M), elemental silicon (Si), especially nanoparticles, pyrolytic carboncoatings (HC), carbon nano fibers (CNF), or combinations thereof. Thus,the general compositions of the composites can be represented asαSiO-βGr-χHC-δM-εCNF-φSi, where α, β, γ, δ, ε, and φ are relativeweights that can be selected such that α+β+γ+δ+ε+φ=1. Generally0.35<α<1, 0≦β<0.6, 0≦χ<0.65, 0≦δ<0.65, 0≦ε<0.65, and 0≦φ<0.65. Certainsubsets of these composite ranges are of particular interest. In someembodiments, composites with SiO and one or more carbon based componentsare desirable, which can be represented by a formula αSiO-βGr-χHC-εCNF,where 0.35<α<0.9, 0≦β≦0.6, 0≦χ<0.65 and 0≦ε≦0.65 (δ=0 and φ=0), infurther embodiments 0.35<α<0.8, 0.1≦β<0.6, 0.0≦χ<0.55 and 0≦ε<0.55, insome embodiments 0.35<α<0.8, 0≦β<0.45, 0.0≦χ<0.55 and 0.1≦ε<0.65, and inadditional embodiments 0.35<α<0.8, 0≦β<0.55, 0.1≦χ<0.65 and 0≦ε<0.55. Inadditional or alternative embodiments, composites with SiO, inert metalpowders and optionally one or more conductive carbon components can beformed that can be represented by the formula αSiO-βGr-χHC-δM-εCNF,where 0.35<α<1, 0≦β<0.55, 0≦χ<0.55, 0.1≦δ<0.65, and 0≦ε<0.55. In furtheradditional or alternative embodiments, composites of SiO with elementalsilicon and optionally one or more conductive carbon components can beformed that can be represented by the formula αSiO-βGr-χHC-εCNF-φSi,where 0.35<α<1, 0≦β<0.55, 0≦χ<0.55, 0≦ε<0.55, and 0.1≦φ<0.65 and infurther embodiments 0.35<α<1, 0≦β<0.45, 0.1≦χ<0.55, 0≦ε<0.45, and0.1≦φ<0.55. A person or ordinary skill in the art will recognize thatadditional ranges within the explicit ranges above are contemplated andare within the present disclosure.

Nanostructured materials can provide high surface areas and/or high voidvolume relative to a corresponding bulk material, such as a siliconoxide based material. By adapting to volume changes of the material, itis believed that nanostructured silicon oxide based material, e.g., nanoparticulates, can provide at least some accommodation for volumeexpansion and reduced stress on the material during silicon-lithiumalloying. Furthermore, the adaptability of nano structured silicon oxidebased materials can result in a corresponding decrease in irreversiblestructural changes in the material upon cycling such that theperformance of the negative electrode degrades more slowly upon cycling,and a battery formed with the negative electrode can have satisfactoryperformance over a larger number of battery cycles. As described hereinmilling can be a suitable process for the formation of nanostructuressilicon oxide based materials, and the milling process can be combinedwith the formation of a composite with a selected electricallyconductive component.

Oxygen deficient silicon oxide with its high specific capacity withrespect to intake and release of lithium and relatively lower volumechange compared to silicon has been studied as negative electrodematerial. As used herein unless specifically noted otherwise, the term“silicon oxide” in reference to a lithium active material as well as“oxygen deficient silicon oxide” refers to amorphous oxygen deficientsilicon oxides generally represented by formula SiO_(x) where 0.1≦x≦1.9,in further embodiments 0.15≦x≦1.8, in other embodiments 0.2≦x≦1.6 and inadditional embodiments 0.25≦x≦1.5. In some embodiments, the x≈1 and thesilicon oxide is represented by formula SiO. A person of ordinary skillin the art will recognize that additional ranges of silicon oxidestoichiometry within the explicit ranges above are contemplated and arewithin the present disclosure. Silicon oxide based materials can containvarious amounts of silicon, silicon oxide, and silicon dioxide. Ingeneral, silicon oxide measured or tested as control without priortreatment is referred to as the “pristine” sample throughout thespecification. The word “pristine” used herein thus refers to untreatedcontrol sample instead of indicating the purity or condition of thecontrol sample.

In some embodiments, the negative electrode active material comprises acomposite of an initially particulate carbon material and a siliconoxide based material. After forming the composite, the silicon oxidebased material can be nanostructured. For example, the components of thecomposite can be milled together to form the composite, in which theconstituent materials are intimately associated, but generally notalloyed or otherwise chemically reacted. The nanostructurecharacteristics are generally expected to manifest themselves in thecomposite, although characterization of the composites may be lessestablished relative to the characterization of the component materials.Specifically, the composite material may have dimensions, porosity orother high surface area characteristics that are manifestations of thenano-scale of the initial materials and/or properties of the materialresulting from milling or other process used in forming the composite.In some embodiments, the negative electrode active material can comprisea silicon oxide based material in a composite with carbon nanofibersand/or carbon nanoparticles, which is achieved using high energymechanical milling.

In some embodiments, the silicon-based negative electrode activematerial can comprise a silicon oxide-metal composite. Siliconoxide-metal composites can be formed from a variety of elemental metalsand generally the elemental metals do not alloy with lithium duringcycling of the corresponding battery. A wide range of metals can beused, as described further below.

Also, carbon coatings can be applied over the silicon oxide basedmaterials to improve electrical conductivity, and the carbon coatingsseem to also stabilize the silicon oxide based material with respect toimproving cycling and decreasing irreversible capacity loss. Inembodiments of particular interest, an organic composition dissolved ina suitable solvent can be mixed with the active composition and dried tocoat the active composition with the carbon coating precursor. Theprecursor coated composition can then be pyrolyzed in an oxygen freeatmosphere to convert the organic precursor into a carbon coating, suchas a hard carbon coating. The carbon coated compositions have been foundto improve the performance of the negative electrode active material.

Without being limited by a theory, it is believed that carbon coatingsand/or composite formulations, especially in a nanostructured form, canprovide structural stability to the expanding and contracting siliconoxide during silicon oxide-lithium intercalation/alloying andcorresponding release of lithium. Desirable battery performance has beenobserved with nanostructured silicon oxide composites as well as withcarbon coated silicon oxide based materials.

Based on the combination of improved parameters described herein, thesilicon oxide based active materials can be introduced to form improvedelectrode structures. In particular, the selection of desirableelectrically conductive components can provide for improved electrodedesign and the desirable polymer binders can provide desired mechanicalproperties suitable for the electrode design in view of significantactive material changes during cycling. Based on these combinedfeatures, silicon oxide based electrodes can be formed with densities ofactive silicon oxide based materials, e.g., composite materials withelectrically conductive components, with at least reasonable performanceof at least about 0.6 g/cm³, in further embodiments at least about 0.7g/cm³ and in further embodiments at least about 0.75 g/cm³. Similarly,the silicon oxide based electrodes can have an average dried thicknessof at least about 25 microns, in further embodiments at least about 30microns and in additional embodiments at least about 50 microns, whichcan correspond to active material loadings of at least about 2 mg/cm².The resulting silicon oxide based electrodes can exhibit capacities perunit area of at least about 3.5 mAh/cm², in further embodiments at leastabout 4.5 mAh/cm² and in additional embodiments at least about 6mAh/cm². A person of ordinary skill in the art will recognize thatadditional ranges of negative electrode parameters within the explicitranges above are contemplated and are within the present disclosure.

Silicon Oxide

In general, any reasonable method can be used to synthesize the siliconoxide for use in the silicon oxide based materials described herein. Atleast SiO is available commercially from Sigma-Aldrich. Furthermore,silicon oxide may be produced, for example, by heating a mixture ofsilicon dioxide and metallic silicon to produce silicon monoxide gas andcooling the gas for precipitation as described for example in, U.S. Pat.No. 6,759,160 to Fukuoka et al. entitled “Silicon oxide powder andmaking method” and U.S. Patent Application No. 2007/0259113 to Kizaki etal. entitled “Silicon monoxide vapor deposition material, silicon powderfor silicon monoxide raw material, and method for producing siliconmonoxide”, both are incorporated herein by reference. Alternatively,molten silicon can react with molecular oxygen to form silicon oxidematerial according to a process described in U.S. Pat. No. 6,759,160 toIwamoto et al. entitled “Negative electrode active material and negativeelectrode using the same and lithium ion secondary battery” and U.S.Patent Application No. 2007/0099436 to Kogetsu et al. entitled “Methodof producing silicon oxide, negative electrode active material forlithium ion secondary battery and lithium ion secondary battery usingthe same”, both are incorporated herein by reference.

A silicon-silicon oxide (SiO_(x)) composite with 0<O/Si<1.0 wasdiscussed in U.S. Patent Application No. 2010/0243951 to Watanabe et al.(herein after Watanabe '951 application) entitled “Negative electrodematerial for nonaqueous electrolyte secondary battery, making method andlithium ion secondary battery”, incorporated herein by reference. TheSiO has been prepared by etching silicon oxide particles in an acidicatmosphere. The SiO formed is then coated with carbon using CH₄ gas atelevated temperature. The composites in Watanabe '951 application showedimproved IRCL, specific capacity, as well as cycling performancecompared to samples formed without the acidic etching. A modifiedprocedure where etching is conducted after carbon coating formation isdescribed in U.S. Patent Application No. 2010/0288970 to Watanabe et al.(herein after Watanabe '970 application) entitled “Negative electrodematerial for nonaqueous electrolyte secondary battery, making method andlithium ion secondary battery”, incorporated herein by reference. Thecomposites in Watanabe '970 application showed improved IRCL andspecific capacity and comparable cycling performance compared to samplesformed without acidic etching. Earlier work utilized a vapor depositionprocess to produce SiO_(x) in U.S. Patent Application No. 2007/0254102to Fukuoka et al (herein after Fukuoka) entitled “Method for producingSiO_(x) (x<1)”, incorporated herein by reference. The Watanabe documentsand the Fukuoka do not teach the specific composites described herein orthe corresponding processes.

The formation of lithium silicates has been described in the context ofmaterials for lithium ion batteries. For example, Silicon-Siliconoxide-lithium (Si—SiO—Li) composite has been discussed in U.S. Pat. No.7,776,473 to Aramata et al. (herein after Aramata) entitled“Silicon-Silicon Oxide-Lithium composite, making method, and non-aqueouselectrolyte secondary cell negative electrode material”, incorporatedherein by reference. In Aramata, silicon oxide is mixed with metalliclithium to undergo disproportionation into silicon and silicon dioxidedoped with lithium and concomitant formation of Li₄SiO₄. The formationof lithium silicate correspondingly is believed to result in formationof a portion of elemental silicon, which can then act as an activematerial in a lithium based battery. The composite formed in Aramata hasimproved cycle performance and decreased IRCL compared to the siliconoxide material without lithium while the specific capacity however hasdecreased significantly. The use of supplemental lithium with siliconoxide based materials is not believed to result in substantial formationof lithium silicate. During electrochemical lithiation, the lithiumintercalates and de-intercalates into and out from the amorphous siliconoxide structure in contrast with the formation of the stable crystallinelithium silicate structure. However, the formation of some lithiumsilicate as a byproduct of the lithiation process herein has not beenruled out, although even with the formation of such byproducts, thelithiation processes described herein are substantially different fromthe processes and compositions described in Aramata.

An early description of oxygen deficient silicon oxide as an activematerial for a lithium ion battery is described in U.S. Pat. No.6,083,644 to Watanabe et al. entitled “Non-aqueous electrolyte secondarybattery,” incorporated herein by reference. Synthesis of silicon oxidewith various amount of carbon coating were discussed in U.S. PatentApplication No. 2004/0033419 to Funabiki et al. (herein after Funabiki)entitled “Negative active material, negative electrode using the same,non-aqueous electrolyte battery using the same, and method for preparingthe same”, incorporated herein by reference. In Funabiki, silicon oxidewas heat treated to form a composite SiO_(x) followed by itching withhydrofluoric acid to remove any SiO₂ in the product material.

Composites of Silicon oxide-graphite (SiO—C) with optional carboncoating were discussed in U.S. Pat. No. 6,638,662 to Kaneda et al.(herein after Kaneda) entitled “Lithium secondary battery having oxideparticles embedded in particles of carbonaceous material as a negativeelectrode material”, incorporated herein by reference. In Kaneda,silicon oxide is ball milled extensively with graphite, which is in turnoptionally coated with carbon through the heating of the silicon oxidewith a carbon precursor in an inert atmosphere.

Lim et al. discussed the use of silicon, silicon oxide, or silicon alloywith carbon in U.S. Patent Application No. 2009/0325061 entitled“Secondary battery”, incorporated herein by reference. Jeong et al.discussed the use of silicon based compound alloyed with metal mixedwith a carbonaceous material in U.S. Pat. Nos. 7,432,015 and 7,517,614,both entitled “Negative active material for a rechargeable lithiumbattery, a method of preparing the same, and a rechargeable lithiumbattery comprising the same”, both incorporated herein by reference. Thesilicon oxide used is formed by heating silicon dioxide with silicon atelevated temperature. Similarly, Lee et al. discussed the use of siliconbased compound alloyed with metal mixed with a carbonaceous material inU.S. Patent Application No. 2005/0233213, entitled “Negative activematerial for a rechargeable lithium battery, a method of preparing thesame, and a rechargeable lithium battery comprising the same”,incorporated herein by reference. The silicon oxide used is formed byheating silicon dioxide with silicon at elevated temperature. Mah et al.disclosed synthesis of SiO_(x) (0<x<0.8) from silane compound in U.S.Patent Application No. 2008/0193831 entitled “Anode active material,method of preparing the same, anode and lithium battery containing thematerial”, incorporated herein by reference. Kim et al. disclosedsynthesis of SiO_(x) (0<x<2) by sintering hydrogen silsesquioxane inU.S. Pat. No. 7,833,662 entitled “Anode active material, method ofpreparing the same, and anode and lithium battery containing thematerial”, incorporated herein by reference.

Composites with Carbon Particles and/or Nano-Scale Carbon Fibers

Carbon nanofibers and/or carbon nanoparticles provide for goodelectrical conductivity and can provide a support structure fornano-structured silicon oxide such that the stress of alloy formationwith lithium can be reduced. Carbon nanofibers can be obtained or can besynthesized using a vapor organic composition and a catalyst in asuitable thermal reaction. One approach for the synthesis of carbonnanofibers are described in published U.S. patent application2009/0053608 to Choi et al., entitled “Anode Active Material HybridizingCarbon Nanofiber for Lithium Secondary Battery,” incorporated herein byreference. Carbon fibers are available commercially from a variety ofsuppliers. Suitable suppliers are summarized in Table 3, which has partsA and B.

In general, suitable carbon nanofibers can have average diameters ofabout 25 nm to about 250 nm and in further embodiments, from about 30 nmto about 200 nm, and with average lengths from about 2 microns to about50 microns, and in further embodiments from about 4 microns to about 35microns. A person of ordinary skill in the art will recognize thatadditional ranges of nanofiber average diameters and lengths within theexplicit ranges above are contemplated and are within the presentdisclosure.

Similarly, pyrolytic carbon particles, e.g., carbon blacks, can be usedas a support in appropriate composites. Carbon black can have averageparticle sizes of no more than about 250 nm, and in some embodiments nomore than about 100 nm, as well as suitable subranges within theseranges. Carbon blacks are readily available from a variety of suppliers,such as Cabot Corporation and Timcal, Ltd, Switzerland (acetylene black,Super P™).

Graphite (Gr), a polymorph of the element carbon, is a semimetal andelectrically conductive. Graphite is also called graphitic carbon orgraphitic particles and can be crystalline with isolated, flat,plate-like particles. Graphite can be milled with silicon oxide with orwithout additional material to form composites having improved capacity.In some embodiments, the composites may contain 0 to 60% wt, 5 to 55%wt, or 10 to 45% wt graphitic carbon. A person or ordinary skill in theart will recognize that additional ranges within the explicit rangesabove are contemplated and are within the present disclosure. Graphitepowders are readily available from a variety of suppliers, such asnatural graphite from Superior Graphite, MAGD™ and MAGE™ artificialgraphite from Hitachi Chemical, MPG-13™ from Mitsubishi, and MCMB™graphite from Nippon Carbon.

It can be desirable to form composites of nano-scale carbon particlesand/or fibers with silicon oxide. To form the composites, theconstituent materials are obtained and/or prepared and combined tointroduce strong mechanical interactions between the materialcomponents. While not wanted to be limited by theory, the composite maycomprise, for example, at least a fraction of the carbon compositioncoated onto silicon oxide that is milled to a submicron scale from theprocessing. In general, the types of interactions between theconstituents of the composites do not need to be well characterized.Nevertheless, the composites are distinct in composition and propertiesfrom simple blends of the constituent materials that may be heldtogether with a binder. The composites though are found to exhibitdesirable battery performance in a lithium ion battery. In general, thecomposite can comprise at least about 5 weight percent silicon oxide, infurther embodiments, from about 7.5 weight percent to about 95 weightpercent and in additional embodiments from about 10 weight percent toabout 90 weight percent silicon oxide. A person of ordinary skill in theart will recognize that additional ranges of silicon oxide compositionwithin the explicit ranges above are contemplated and are within thepresent disclosure.

In some embodiments, silicon oxide composites can be formed by millingsilicon oxide with carbon fibers and/or carbon nanoparticles. Themilling process can comprise, for example, jar milling and/or ballmilling, such as planetary ball milling. Ball milling and similarly jarmilling may involve grinding using a grinding medium, such as ceramicparticles, which can then be substantially removed from the groundmaterial. A planetary ball mill is a type of ball milling in which themill comprises a sun-wheel, at least one grinding jar mountedeccentrically on the sun-wheel, and a plurality of mixing balls withinthe grinding jar. In operation, the grinding jar rotates about its ownaxis and in the opposite direction around the common axis of thesun-wheel.

Desirable ball milling rotation rates and ball milling times can beselected based on the desired silicon oxide composite composition andstructure. For the formation of silicon oxide composites describedherein, suitable ball milling rotation rates generally can be from about25 rpm to about 1000 rpm and in further embodiments from about 50 rpm toabout 800 rpm. Furthermore, desirable ball milling times can be fromabout 10 minutes to about 20 hour, in further embodiments from about 20minutes to about 15 hours, in additional embodiments from about 1 hourto 5 hours. A person of ordinary skill in the art will recognize thatadditional ranges of milling rates and times within the explicit rangesabove are contemplated and are within the present disclosure. The millcontainer can be filled with an inert gas to avoid oxidizing thecontents of the container during milling. Examples of suitable grindingmedia include, for example, particles of zirconia, alumina, tungstencarbide or the like.

The milling of the silicon oxide based materials results in a reducedparticle size that seems to contribute significantly to performancebased on the milling of the particles. The desirable performance can beachieved similarly with the performance of the milling with electricallyconductive particles for the formation of a composite. In general, themilled particles can be evaluated with respect to size by forming adispersion and using light scattering to measure particle size. Directmeasurements by dynamic light scattering (DLS) are intensity weightedparticle size distributions, and these can be converted to volume baseddistributions using conventional techniques. The volume-average particlesize can be evaluated from the volume-based particle size distribution.Suitable particle size analyzers include, for example, a Microtrac UPAinstrument from Honeywell and Saturn DigiSizer™ from Micromeritics basedon dynamic light scattering, a Horiba Particle Size Analyzer fromHoriba, Japan and ZetaSizer Series of instruments from Malvern based onPhoton Correlation Spectroscopy. The principles of dynamic lightscattering for particle size measurements in liquids are wellestablished. The volume average particle sizes can be no more than about10 microns, in other embodiments no more than about 8 microns and infurther embodiments no more than about 7 microns. A person of ordinaryskill in the art will recognize that additional ranges of averageparticle size within the explicit ranges above are contemplated and arewithin the present disclosure.

Metal Particle—Silicon Oxide Composites

Inert metal particles are also useful for the formation of compositeswith the silicon oxide materials. The incorporation of the metal intothe composite can improve the electrical conductivity of the compositematerial. The metal for these composites is generally selected to beinert with respect to reaction both with silicon oxide so that the metaldoes not reduce the silicon oxide and with lithium so that the metaldoes not alloy with lithium under conditions to be experienced in thebatteries. The composites are formed through high energy milling or thelike to intimately combine the materials in the composite so that thematerials are distinctly different from simple blend of the materialthat may be held together by a polymer. In the composite materials,while not wanting to be limited by theory, the more malleable metal maybe spread over the silicon oxide material during the formation of thecomposite.

The inert metal-silicon oxide composites are found to exhibit desirablebattery performance in a lithium ion battery. Suitable metals include,for example, nickel, iron, vanadium, cobalt, titanium, zirconium,silver, manganese, molybdenum, gallium, chromium and combinationsthereof. In general, the composite can comprise at least about 5 weightpercent silicon oxide, in further embodiments, from about 7.5 weightpercent to about 95 weight percent and in additional embodiments fromabout 10 weight percent to about 90 weight percent silicon oxide.Similarly, in some embodiments, the composite can comprise from about 5to about 45 weight percent inert metal and in further embodiments fromabout 7 to about 40 weight percent inert metal. A person of ordinaryskill in the art will recognize that additional ranges of silicon oxidecomposition within the explicit ranges above are contemplated and arewithin the present disclosure.

The inert-metal-silicon oxide composites can be formed using high energymechanical milling similar to the formation of the carbon-silicon oxidecomposites. A ball media generally is used with the metal particles tofacilitate the milling process. Desirable milling rotation rates andmilling times can be selected based on the desired inert metal-siliconoxide composite composition and structure. For the formation of siliconoxide composites described herein, suitable milling rotation ratesgenerally can be from about 25 rpm to about 1000 rpm and in furtherembodiments from about 50 rpm to about 800 rpm. Furthermore, desirablemilling times can be from about 10 minutes to about 50 hour and infurther embodiments from about 20 minutes to about 20 hours. A person ofordinary skill in the art will recognize that additional ranges ofmilling rates and times within the explicit ranges above arecontemplated and are within the present disclosure. The mill containercan be filled with an inert gas to avoid oxidizing the contents of thecontainer during milling.

Pyrolytic Carbon Coatings

Carbon coatings can be applied to silicon oxide based material toincrease electrical conductivity and/or to provide structural support tothe resulting materials. In general, the carbon coatings can be appliedto silicon oxide, for example, after milling the silicon oxide, siliconoxide carbon particle composites, silicon oxide-metal particlecomposites or the like. The carbon coatings can be formed from pyrolyzedorganic compositions under oxygen free atmospheres. Hard carbon coatingsare generally formed at relatively high temperatures. The properties ofthe coatings can be controlled based on the processing conditions. Inparticular, carbon coatings can have a high hardness and generally cancomprise significant amorphous regions possible along with graphiticdomains and diamond structured domains.

Carbon coatings formed from coal tar pitch is described in published PCTpatent application WO 2005/011030 to Lee et al., entitled “A NegativeActive Material for Lithium Secondary Battery and a Method for PreparingSame,” incorporated herein by reference. In contrast, as describedherein, an organic composition is dissolved in a suitable solvent andmixed with the active material. The solvent is removed through drying toform a solid precursor coated active material. This approach with asolvent for delivering a solid pyrolytic carbon precursor can facilitateformation of a more homogenous and uniform carbon coating. Then, theprecursor coated material is heated in an effectively oxygen freeenvironment to form the pyrolytic carbon coating.

The heating is generally performed at a temperature of at least about500° C., and in further embodiments at least about 700° C. and in otherembodiments, from about 750° C. to about 1350° C. Generally, iftemperatures are used above about 800° C., a hard carbon coating isformed. The heating can be continued for a sufficient period of time tocomplete the formation of the carbon coating. In some embodiments, it isdesirable to use pyrolytic carbon precursors that can be delivered in asolvent to provide for good mixing of the precursors with the siliconoxide based materials and to provide for a range of desired precursorcompounds. For example, desirable precursors can comprise organiccompositions that are solids or liquids at room temperature and havefrom two carbon atoms to 40 carbon atoms, and in further embodimentsfrom 3 carbon atoms to 25 carbon atoms as well as other ranges of carbonatoms within these ranges, and generally these molecules can compriseother atoms, such as oxygen, nitrogen, sulfur, and other reasonableelements. Specifically, suitable compounds include, for example, sugars,other solid alcohols, such as furfuryl alcohol, solid carboxylic acids,such as citric acid, polymers, such as polyacrylonitrile, and the like.The coated materials generally comprise no more than about 50 weightpercent pyrolytic carbon, in further embodiments no more than about 40weight percent, and in additional embodiments, from about 1 weightpercent to about 30 weight percent. A person of ordinary skill in theart will recognize that additional ranges within the explicit rangesabove of amounts of coating composition are contemplated and are withinthe present disclosure.

Metal Coatings

As an alternative or in addition to carbon coatings, elemental metal canbe coated onto the silicon oxide based material. For example, the metalcoatings can be applied to silicon-oxide carbon composites, siliconoxide-metal particle composites or the like. Suitable elemental metalsinclude metals that can be reduced under reasonable conditions to forman inert metal in the battery. In particular, silver and copper can bereduced to deposit the metal coating. The elemental metal coating can beexpected to increase electrical conductivity and to stabilize thesilicon oxide based material during the lithium alloying and de-alloyingprocess. In general, the coated material can comprise no more than about25 weight percent metal coating and in further embodiments from about 1weight percent to about 20 weight percent metal coating. A person ofordinary skill in the art will recognize that additional ranges of metalcoating composition within the explicit ranges above are contemplatedand are within the present disclosure. A solution based approach can beused to apply the metal coating. For example, the silicon oxide basedmaterial to be coated can be mixed with a solution comprising dissolvedsalt of the metal, such as silver nitrate, silver chloride, coppernitrate, copper chloride or the like, and a reducing agent can be addedto deposit the metal coating. Suitable reducing agents include, forexample, sodium hypophosphite, sodium borohydride, hydrazine,formaldehyde and the like.

Supplemental Lithium

Various approaches can be used for the introduction of supplementallithium into the battery, although following corresponding initialreactions and/or charging, the negative electrode becomes associatedwith excess lithium for cycling from the supplemental lithium. Withrespect to the negative electrode in batteries having supplementallithium, the structure and/or composition of the negative electrode canchange relative to its initial structure and composition following thefirst cycle as well as following additional cycling. Depending on theapproach for the introduction of the supplemental lithium, the positiveelectrode may initially include a source of supplemental lithium and/ora sacrificial electrode can be introduced comprising supplementallithium. The supplemental lithium is introduced into the negativeelectrode using electrochemical methods in contrast with purely chemicalor mechanical methods. Chemical methods or mechanical methods, such asmilling, may lead to effectively irreversible formation of lithiumsilicate, while the electrochemical method does not seem to result inlithium silicate formation. In particular, the electrochemicalintroduction of lithium in general results in reversible lithiumincorporation, although lithium can be consumed in an initial formationof a solvent electrolyte interphase (SEI) layer. With respect to initialstructure of the negative electrode, in some embodiments, the negativeelectrode has no changes due to the supplemental lithium. In particular,if the supplemental lithium is initially located in the positiveelectrode or a separate electrode, the negative electrode can be anunaltered form with no lithium present until the battery is charged orat least until the circuit is closed between the negative electrode andthe electrode with the supplemental lithium in the presence ofelectrolyte and a separator. For example, the positive electrode orsupplemental electrode can comprise elemental lithium, lithium alloyand/or other sacrificial lithium source.

If sacrificial lithium is included in the positive electrode, thelithium from the sacrificial lithium source is loaded into the negativeelectrode during the charge reaction. The voltage during the chargingbased on the sacrificial lithium source may be significantly differentthan the voltage when the charging is performed based on the positiveelectrode active material. For example, elemental lithium in thepositive electrode can charge the negative electrode active materialwithout application of an external voltage since oxidation of theelemental lithium drives the reaction. For some sacrificial lithiumsource materials, an external voltage is applied to oxidize thesacrificial lithium source in the positive electrode and drive lithiuminto the negative electrode active material. The charging generally canbe performed using a constant current, a stepwise constant voltagecharge or other convenient charging scheme. However, at the end of thecharging process, the battery should be charged to a desired voltage,such as 4.5V.

In further embodiments, at least a portion of the supplemental lithiumis initially associated with the negative electrode. For example, thesupplemental lithium can be in the form of elemental lithium, a lithiumalloy or other lithium source that is more electronegative than thenegative electrode active material. After the negative electrode is incontact with electrolyte, a reaction can take place, and thesupplemental lithium is transferred to the negative electrode activematerial. During this process, the solid electrolyte interface (SEI)layer is also formed. Thus, the supplemental lithium is loaded into thenegative electrode active material with at least a portion consumed information of the SEI layer. The excess lithium released from the lithiumrich positive electrode active material is also deposited into thenegative electrode active material during eventual charging of thebattery. The supplemental lithium placed into the negative electrodeshould be more electronegative than the active material in the negativeelectrode since there is no way of reacting the supplemental lithiumsource with the active material in the same electrode through theapplication of a voltage.

In some embodiments, supplemental lithium associated with the negativeelectrode can be incorporated as a powder within the negative electrode.Specifically, the negative electrode can comprise an active negativeelectrode composition and a supplemental lithium source within a polymerbinder matrix, and any electrically conductive powder if present. Inadditional or alternative embodiments, the supplemental lithium isplaced along the surface of the electrode. For example, the negativeelectrode can comprise an active layer with an active negative electrodecomposition and a supplemental lithium source layer on the surface ofactive layer. The supplemental lithium source layer can comprise a foilsheet of lithium or lithium alloy, supplemental lithium powder within apolymer binder and/or particles of supplemental lithium source materialembedded on the surface of the active layer. In an alternativeconfiguration, a supplemental lithium source layer is between the activelayer and current collector. Also, in some embodiments, the negativeelectrode can comprise supplemental lithium source layers on bothsurfaces of the active layer.

In additional embodiments, at least a portion of the supplementallithium can be supplied to the negative electrode active material priorto assembly of the battery. In other words, the negative electrode cancomprise partially lithium-loaded silicon oxide based active material,in which the partially loaded active material has a selected degree ofloading of lithium through intercalation/alloying or the like. Forexample, for the preloading of the negative electrode active material,the negative electrode active material can be contacted with electrolyteand a lithium source, such as elemental lithium, lithium alloy or othersacrificial lithium source that is more electronegative than thenegative electrode active material.

An arrangement to perform such a preloading of lithium can comprise anelectrode with silicon oxide based active material formed on a currentcollector, which are placed in vessel containing electrolyte and a sheetof lithium source material contacting the electrode. The sheet oflithium source material can comprise lithium foil, lithium alloy foil ora lithium source material in a polymer binder optionally along with anelectrically conductive powder, which is in direct contact with thenegative electrode to be preloaded with lithium such that electrons canflow between the materials to maintain electrical neutrality while therespective reactions take place. In the ensuing reaction, lithium isloaded into the silicon oxide based active material throughintercalation, alloying or the like. In alternative or additionalembodiments, the negative electrode active material can be mixed in theelectrolyte and the lithium source material for incorporation of thesupplemental lithium prior to formation into an electrode with a polymerbinder so that the respective materials can react in the electrolytespontaneously.

In some embodiments, the lithium source within an electrode can beassembled into a cell with the electrode to be preloaded with lithium. Aseparator can be placed between the respective electrodes. Current canbe allowed to flow between the electrodes. Depending on the compositionof the lithium source it may or may not be necessary to apply a voltageto drive the lithium deposition within the silicon oxide based activematerial. An apparatus to perform this lithiation process can comprise acontainer holding electrolyte and a cell, which comprises an electrode,to be used as a negative electrode in an ultimate battery, a currentcollector, a separator and a sacrificial electrode that comprises thelithium source, where the separator is between the sacrificial electrodeand the electrode with the silicon-based active material. A convenientsacrificial electrode can comprise lithium foil, lithium powder embeddedin a polymer or lithium alloys, although any electrode with extractablelithium can be used. The container for the lithiation cell can comprisea conventional battery housing, a beaker, or any other convenientstructure. This configuration provides the advantage of being able tomeasure the current flow to meter the degree of lithiation of thenegative electrode. Furthermore, the negative electrode can be cycledonce or more than once in which the negative electrode active materialis loaded close to full loading with lithium. In this way, an SEI layercan be formed with a desired degree of control during the preloadingwith lithium of the negative electrode active material. Then, thenegative electrode is fully formed during the preparation of thenegative electrode with a selected preloading with lithium.

In general, the lithium source can comprise, for example, elementallithium, a lithium alloy or a lithium composition, such as a lithiummetal oxide, that can release lithium from the composition. Elementallithium can be in the form of a thin film, such as formed byevaporation, sputtering or ablation, a lithium or lithium alloy foiland/or a powder. Elemental lithium, especially in powder form, can becoated to stabilize the lithium for handling purposes, and commerciallithium powders, such as powders from FMC Corporation, are sold withproprietary coatings for stability. The coatings generally do not alterthe performance of the lithium powders for electrochemical applications.Lithium alloys include, for example, lithium silicon alloys and thelike. Lithium composition with intercalated lithium can be used in someembodiments, and suitable compositions include, for example, lithiumtitanium oxide, lithium tin oxide, lithium cobalt oxide, lithiummanganese oxide, and the like.

In general, for embodiments in which supplemental lithium is used, theamount of supplemental lithium preloaded or available to load into theactive composition can be in an amount of at least about 2.5% ofcapacity, in further embodiments from about 3 percent to about 90percent of capacity, in additional embodiments from about 5 percent toabout 80 percent of capacity, and in some embodiments at least 10% ofthe negative electrode active material capacity. The supplementallithium can be selected to approximately balance the IRCL of thenegative electrode, although other amounts of supplemental lithium canbe used as desired. Thus, the contribution to the IRCL of the negativeelectrode can be effectively reduced or removed due to the addition ofthe supplemental lithium such that the measured IRCL of the batteryrepresents partially or mostly contributions from the IRCL of thepositive electrode, which is not diminished due to the presence ofsupplemental lithium. In some embodiments, the IRCL can be reduced to nomore than about 20% of the initial negative electrode capacity, infurther embodiments no more than about 15%, in additional embodiments nomore than about 10%. A person of ordinary skill in the art willrecognize that additional ranges of IRCL within the explicit rangesabove are contemplated and are within the present disclosure.

Another parameter of interest relates to the total balance of thecapacity of the negative electrode active material against the positiveelectrode theoretical capacity, when supplemental lithium is present. Ithas been observed that the inclusion of additional negative electrodecapacity can be desirable when supplemental lithium is present tocompensate for all or some of the IRCL of the negative electrode. Insome embodiments, the balance expressed as a ratio of negative electrodecapacity divided by positive electrode capacity expressed as a percentcan be from about 95 to about 180 percent of the negative electrodecapacity, in further embodiments from about 100 to about 160 percent andin other embodiments, from about 110 percent to about 150 percent.Furthermore, increased values of average voltage are observed when thebattery comprises supplemental lithium. Specifically, for batteries withSiO based active materials a supplemental lithium, the average voltagecan be at least about 3.3V, in further embodiments at least above 3.35Vand in other embodiments from 3.37V to about 3.45V when cycled between4.5V and 2.0V at rates of C/3. A person of ordinary skill in the artwill recognize that additional ranges of battery balance within theexplicit ranges above are contemplated and are within the presentdisclosure.

Battery Performance

Batteries formed from lithium rich positive electrode active materials,silicon oxide based negative electrode active materials, with or withoutsupplemental lithium have demonstrated promising performance underrealistic discharge conditions. Specifically, the silicon oxide basednegative electrode active materials have demonstrated a high specificcapacity upon cycling of the batteries at moderate discharge rates andwith realistic cathodes with cycling over a voltage range with a highvoltage cutoff. In particular, desirable specific capacities can beobtained based on both the masses of the positive electrode activematerial and the negative electrode active material such that theresults correspond with a high overall capacity of the batteries.Silicon based negative electrode composites described herein can exhibitreasonable irreversible capacity losses, and in some embodimentssupplemental lithium can be successfully used to reduce the irreversiblecapacity loss. Electrode balance to reduce irreversible capacity loss isdescribed above. Relatively stable cycling of the silicon based negativeelectrode material at high specific capacities can be obtained for amodest number of cycles against a positive electrode with lithium richhigh capacity lithium metal oxides.

In general, various similar testing procedures can be used to evaluatethe capacity performance of the battery. The silicon oxide basedelectrodes can be tested against a lithium foil electrode to evaluatethe capacity and the IRCL. However, more meaningful testing can beperformed with a realistic positive electrode since then the battery iscycled over appropriate voltage ranges for cycling in a useful battery.Suitable testing procedures are described in more detail in the examplesbelow. Specifically, batteries assembled with a lithium foil electrodeare cycled with the silicon oxide based electrode functioning as apositive electrode (cathode) and the lithium foil functions as thenegative electrode (anode). The batteries with a lithium foil electrodecan be cycled over a voltage range, for example, from 0.005V to 1.5 V atroom temperature. Alternatively, batteries can be formed with a positiveelectrode comprising a layered-layered lithium rich metal oxide in whichthe silicon oxide based electrode is then the negative electrode, andthe battery can then be cycled between 4.5 volts and 1.0 volt at roomtemperature. For the batteries with a lithium metal oxide-based positiveelectrode, the first cycle can be charged and discharged at a rate ofC/20 and subsequent cycling can be at a rate of C/3 unless specifiedotherwise with charging at C/3. The specific discharge capacity is verydependent on the discharge rate. The notation C/x implies that thebattery is discharged at a rate to fully discharge the battery to theselected voltage minimum in x hours.

The specific capacity of the silicon oxide based negative electrode canbe evaluated in configurations with either a lithium-foilcounter-electrode or with a lithium metal oxide based counter electrode.For the batteries formed with a lithium metal oxide based positiveelectrode, the specific capacity of the battery can be evaluated againstthe weights of both anode active material and cathode active material,which involved division of the capacity by the respective weights. Ifsupplemental lithium is included in the battery, the weight of thenegative electrode active material includes the weight of thesupplemental lithium. Using a high capacity positive electrode activematerial, the overall benefits of using a high capacity silicon oxidebased negative electrode active material becomes even more beneficial.Based on the capacity of the battery, the specific capacities can beobtained by dividing the respective weight of the active materials ineach electrode. It can be desirable to have high specific capacities forboth electrodes. The advantages of high specific capacity for eachelectrode with respect to the overall specific capacity of the batteryis described in an article by Yoshio et al., Journal of Power Sources146 (June 2005) pp 10-14, incorporated herein by reference.

In general, it can be desirable for the negative electrode to have aspecific capacity at the tenth cycle of at least about 500 mAh/g, infurther embodiments at least about 700 mAh/g, in some embodiments atleast about 850 mAh/g, in additional embodiments at least about 1000mAh/g, and in some embodiments at least about 1100 mAh/g at a dischargerate of C/3 when cycled between 4.5V and 1.0V based on the anode activeweight. Depending on the specific silicon oxide based active material,the lower voltage cutoff can be selected to be 2.0V, 1.5V, 1.0V or 0.5V.In general, the lower voltage cutoff can be selected to extract aselected portion of the electrode capacity from about 92% to about 99%,and in further embodiments from about 95% to about 98% of the totalcapacity of the positive electrode. As noted above, it can be desirableto have a relatively high specific capacity for both electrodes when thepositive electrode comprises a lithium rich metal oxide, and the batterycan exhibit at a discharge rate of C/3 at the 50th cycle a positiveelectrode specific capacity of at least about 150 mAh/g and a negativeelectrode specific capacity of at least about 750 mAh/g, in furtherembodiments a positive electrode specific capacity of at least about 160mAh/g and a negative electrode specific capacity of at least about 800mAh/g, and in additional embodiments a positive electrode specificcapacity of at least about 170 mAh/g and a negative electrode specificcapacity of at least about 1000 mAh/g, when cycled between 4.5V and1.0V. The batteries with lithium rich metal oxides and silicon oxidebased materials can exhibit desirable cycling properties, and inparticular the batteries can exhibit a discharge capacity decrease of nomore than about 15 percent at the 50th discharge cycle relative to the7th discharge cycle and in further embodiments no more than about 10percent when discharged at a rate of C/3 from the 7th cycle to the 50thcycle. A person of ordinary skill in the art will recognize thatadditional ranges of specific capacity and other battery parameterswithin the explicit ranges above are contemplated and are within thepresent disclosure. In some embodiments, the batteries further includesupplemental lithium to reduce the irreversible capacity loss and tostabilize the cycling of lithium rich metal oxides.

EXAMPLES

A significant variety of silicon oxide based active negative electrodematerials were tested in batteries to evaluate their performance. Manyof these samples comprised silicon oxide and some of these samples wereformed into composites with carbon and/or metal powders. Generally, thesamples were formed into coin cells to test the performance of materialswith respect to lithium alloying/intercalation. Coin cells were formedeither with lithium foil as the counter electrode such that the siliconoxide based electrode functioned as a positive electrode against thelithium foil or with a positive electrode comprising a lithium richmixed metal oxide such that the resulting battery had a realisticformulation for cycling over a relevant voltage range for a commercialbattery. The general procedure for formation of the coin cells isdescribed in the following discussion and the individual examples belowdescribe formulation of the silicon oxide based materials and theperformance results from batteries formed from the silicon oxidematerials. The batteries described herein in general were cycled bycharging and discharging between 4.6V and 1.0V in the first formationcycle and between 4.5V and 1.0V in the cycle testing for batteries withHCMR™ positive electrode or between 0.005V-1.5V for batteries withlithium foil counter electrode at a rate of C/20, C/10, C/5, and C/3 forthe 1st and 2nd cycles, for the 3rd and 4th cycles, for the 5th and 6thcycles, and for subsequent cycles, respectively.

To test particular samples, electrodes were formed from the samples ofsilicon oxide based active materials. In general, a powder of siliconoxide based active material was mixed thoroughly with acetylene black(Super P® from Timcal, Ltd., Switzerland) to form a homogeneous powdermixture. Separately, polyimide binder was mixed withN-methyl-pyrrolidone (“NMP”) (Sigma-Aldrich) and stirred overnight toform a polyimide-NMP solution. The homogenous powder mixture was thenadded to the polyimide-NMP solution and mixed for about 2 hours to forma homogeneous slurry. The slurry was applied onto a copper foil currentcollector to form a thin, wet film and the laminated current collectorwas dried in a vacuum oven to remove NMP and to cure the polymer. Thelaminated current collector was then pressed between rollers of a sheetmill to obtain a desired lamination thickness. The dried laminatecontained at least 75 wt % silicon oxide based active material and atleast 2 wt % polyimide binder. The resulting electrodes were assembledwith either a lithium foil counter electrode or with a counter electrodecomprising a lithium metal oxide (LMO).

For a first set of batteries with the lithium foil counter electrodes,the silicon oxide based electrodes were placed inside an argon filledglove box for the fabrication of the coin cell batteries. Lithium foil(FMC Lithium) having thickness of roughly 125 micron was used as anegative electrode. A conventional electrolyte comprising carbonatesolvents, such as ethylene carbonate, diethyl carbonate and/or dimethylcarbonate, was used. A trilayer(polypropylene/polyethylene/polypropylene) micro-porous separator (2320from Celgard, LLC, NC, USA) soaked with electrolyte was placed betweenthe positive electrode and the negative electrode. A few additionaldrops of electrolyte were added between the electrodes. The electrodeswere then sealed inside a 2032 coin cell hardware (Hohsen Corp., Japan)using a crimping process to form a coin cell battery. The resulting coincell batteries were tested with a Maccor cycle tester to obtaincharge-discharge curve and cycling stability over a number of cycles.

For a second set of batteries, the silicon oxide based electrodes wereused as negative electrode, and the positive electrodes comprised a highcapacity lithium rich composition. The resulting positive electrodes arereferred to as high capacity manganese rich (“HCMR™”) electrodes. LMOcomposite active materials were synthesized using a selectedco-precipitation process. The synthesis of similar compositions by ahydroxide co-precipitation process have been described in published U.S.patent application 2010/0086853A to Venkatachalam et al. entitled“Positive Electrode Material for Lithium Ion Batteries Having a HighSpecific Discharge Capacity and Processes for the Synthesis of theseMaterials”, and the synthesis of similar compositions by a carbonateco-precipitation process have been described in published U.S. patentapplication 2010/0151332A to Lopez et al. entitled “Positive ElectrodeMaterials for High Discharge Capacity Lithium Ion Batteries”, both ofwhich are incorporated herein by reference. In particular, the LMOpowder was synthesized that is approximately described by the formulaxLi₂MnO₃.(1−x)Li Ni_(u)Mn_(v)Co_(w)O₂ where x=0.5. A discussion of thedesign of HCMR™ compositions to achieve particular performance resultsare described in detail in published U.S. patent application number2011/0052981 filed Aug. 27, 2010 to Lopez et al., entitled “Layer-LayerLithium Rich Complex Metal Oxides With High Specific Capacity andExcellent Cycling,” incorporated herein by reference.

Electrodes were formed from the synthesized HCMR™ powder by initiallymixing it thoroughly with conducting carbon black (Super P™ from Timcal,Ltd, Switzerland) and graphite (KS 6™ from Timcal, Ltd) to form ahomogeneous powder mixture. Separately, Polyvinylidene fluoride PVDF(KF1300™ from Kureha Corp., Japan) was mixed with N-methyl-pyrrolidone(Sigma-Aldrich) and stirred overnight to form a PVDF-NMP solution. Thehomogeneous powder mixture was then added to the PVDF-NMP solution andmixed for about 2 hours to form homogeneous slurry. The slurry wasapplied onto an aluminum foil current collector to form a thin, wet filmand the laminated current collector was dried in vacuum oven at 110° C.for about two hours to remove NMP. The laminated current collector wasthen pressed between rollers of a sheet mill to obtain a desiredlamination thickness. The dried electrode comprised at least about 75weight percent active metal oxide, at least about 1 weight percentgraphite, and at least about 2 weight percent polymer binder.

Some of the batteries fabricated from a silicon oxide based negativeelectrode and a HCMR™ positive electrode further comprised supplementallithium. In particular, a desired amount of SLMP® powder (FMC Corp.,stabilized lithium metal powder) was loaded into a vial and the vial wasthen capped with a mesh comprising nylon or stainless steel with a meshsize between about 40 μm to about 80 μm. SLMP® (FMC corp.) was thendeposited by shaking and/or tapping the loaded vial over a formedsilicon oxide based negative electrode. The coated silicon oxide basednegative electrode was then compressed to ensure mechanical stability.

Batteries fabricated from a silicon oxide based negative electrode and aHCMR™ positive electrode were balanced to have excess negative electrodematerial. Specific values of the negative electrode balance are providedin the specific examples below. For batteries containing supplementallithium, balancing was based on the ratio of the first cycle lithiuminsertion capacity of the silicon oxide based negative electrode to thetheoretical capacity of the HCMR™ positive electrode. The amount ofsupplemental lithium was selected to approximately compensate for theirreversible capacity loss of the negative electrode. For batterieswithout supplemental lithium, balancing was calculated as the firstcycle lithium insertion capacity of the silicon oxide based negativeelectrode to the theoretical capacity of the HCMR™ positive electrode aswell. In particular, for a given silicon oxide based active composition,the insertion and extraction capacities of the silicon oxide basedcomposition can be evaluated with the battery having a positiveelectrode comprising the silicon oxide based active material and alithium foil negative electrode where lithium is intercalated/alloyed tothe silicon oxide based electrode to 5 mV and de-intercalated/de-alloyedto 1.5V at a rate of C/20.

Coin cell batteries were formed by placing the silicon oxide basedelectrode and the HCMR™ electrode inside an argon filled glove box. Anelectrolyte was selected to be stable at high voltages, and appropriateelectrolytes are described in copending U.S. patent application Ser. No.12/630,992 now U.S. Pat. No. 8,993,177 to Amiruddin et al., entitled“Lithium Ion Battery With High Voltage Electrolytes and Additives,”incorporated herein by reference. Based on these electrodes and the highvoltage electrolyte, the coin cell batteries were completed withseparator and hardware as described above for the batteries with thelithium foil electrode. During the first cycle, the batteries werecharged to 4.6V, and in subsequent cycles, the batteries were charged to4.5V.

Example 1: Silicon Oxide Based Anode Material

This example studies the effect of high energy mechanical milling (HEMM)and heat treatment on the silicon oxide based electrode active material.The silicon oxide starting materials used herein are 325 mesh particlesfrom Sigma-Aldrich. In general, HEMM was used to reduce particle size ofthe starting SiO materials. HEMM process was found to not only reducethe size of SiO but also partially crystallize amorphous SiO to form amaterial comprising some crystalline Si. High temperature heat treatmentof silicon oxide based anode active material has also been shown topartially crystallize amorphous SiO to form some crystalline Si as wellas carbonize a carbon precursor coating material to pyrolytic carbonconcomitantly. HEMM has been used in the subsequent examples below toform composites of silicon oxide powder (325 mesh) with conductivematerial such as graphite, hard carbon, carbon nano-fiber, and metal toincrease the performance and the loading level of silicon oxide basedelectrode active materials.

Micron size silicon oxide (325 mesh) was incorporated into coin cellswith a lithium foil electrode to evaluate its capacity and cyclingbehavior. FIG. 2 is plots of the 1^(st) and 2^(nd) cycle charge anddischarge profile of micron size silicon oxide without milling, showinglarge irreversible capacity loss (IRCL). Electrode with micron sizesilicon oxide at different loading densities 2.73 mg/cm², 4.48 mg/cm²,and 5.26 mg/cm² were cycled and the results are shown in FIG. 3.Batteries incorporating electrodes with silicon oxide loading density of2.73 mg/cm² were observed to have better specific capacity thanbatteries having electrodes with silicon oxide loading densities of 4.48mg/cm² and 5.26 mg/cm². Although significant capacity loss and generallypoor cycling behavior has been observed for electrodes with all threeloading densities for these active materials.

Pristine silicon oxide (325 mesh, Sigma Aldrich) was HEMM ball milled at300 rpm (revolutions per minute) for 1 to 24 h in ethanol and thephysical and cycling behavior of the resulted materials were studied.XRD measurements of these materials with milling times t1-t4 with 1h<t1<t2<t3<t4<24 h shown in FIG. 4 revealed peaks for crystallinesilicon (indicated by black dot) in t2, t3, and t4 samples, indicatingat least partial conversion of the amorphous silicon oxide tocrystalline silicon after sufficient hours of milling. At extended HEMMball milling time of t4, ZrO₂ contaminants from the HEMM media wasobserved in the treated sample, indicating the prolonged millingcondition may not be favored since ZrO₂ would correspond to an inertcontaminant in the active material.

The size distribution of these silicon oxide materials was studied andthe results are shown in FIG. 5. The particle sizes were measured usingdynamic light scattering for particle dispersions. Specifically, longertime HEMM such as t2 or t3 has produced silicon oxide composite withreduced particle size, including particles with less than micron size.Coin cell batteries were formed with these silicon oxide based materialswith a lithium foil counter electrode. The cycling performance of thebatteries with these silicon oxide based materials was evaluated and theresults are shown in FIG. 6. Milling at 300 rpm for t1 and t2 hasproduced silicon oxide composite materials with comparable cyclingperformance, which is significantly better than untreated silicon oxide(labeled pristine). Milling at 300 rpm for t3 produced silicon oxidecomposite materials with the highest specific capacity, better than t1and t2 samples, although the battery with the t3 sample experienced thelargest percent capacity fade. Prolonged milling at t4 resulted in amaterial with poorer battery performance, again indicating the prolongedmilling condition is not favored. HEMM milling at appropriate rate andlength of time therefore improves the cycling behavior of silicon oxide.As micron size silicon oxide particles have shown above in FIGS. 2 and 3to have poor cycling behavior, HEMM milling has been demonstrated tosignificantly improve the battery performance of the material, althoughit is not clear if this improvement is a result of the decrease inparticle size and change in the crystal structure or a combination offactors.

To study the effect of heat treatment, silicon oxide and silicon oxidecoated with an appropriate carbon source were heated in a furnace in aninert atmosphere per condition provided in table 4. Examples of suitablecarbon source are polyvinyl chloride, poly(vinyl chloride)-co-vinylacetate, polyacrylonitrile (PAN), glucose, sucrose, polymerized furfurylalcohol, poly[(o-cresyl glycidyl ether)-co-formaldehyde resin,poly(methacrylo-nitrile). The desired organic compositions can bedissolved in a suitable solvent, such as water and/or volatile organicsolvents, such as NMP (N-Methyl-2-pyrrolidone) and/or THF(tetrahydrofuran).

TABLE 4 Temperature Time Condition 1 600° C. to 1200° C. 1 hr to 24 hr(No Carbon coating) Condition 2 600° C. to 1200° C. 1 hr to 24 hr(Coated with carbon source)

Silicon oxide coated with the appropriate carbon source is known to formsilicon oxide coated pyrolytic carbon, e.g., hard carbon, under thespecified heat treatment conditions to form a SiO—HC composite material.Heat treated samples together with untreated (pristine) silicon oxideare evaluated with XRD measurements and the results are shown in FIG. 7.Silicon oxide particles without the heat treatment appear to compriselargely of amorphous silicon oxide. Heat treated silicon oxide appear tohave similar XRD profile to SiO—HC material, with at least some of theamorphous silicon oxide reduced to crystalline silicon (indicated byblack dots). The cycling performance of the heat treated and untreatedsamples are measured, and the results are shown in FIG. 8. Batteriesformed with heat treated silicon oxide sample without carbon coatingwere observed to have worse cycling performance than batteries formedwith untreated silicon oxide samples, while batteries formed with theSiO—HC material has shown significantly improved cycling behaviorcompared to batteries formed with the untreated sample.

Example 2: Effect of Fluorinated Electrolyte Additive (FEA)

Varied amount of fluorinated electrolyte additive was added to theelectrolyte to investigate the effect of the additive on batteryperformance. Various fluorine containing additives can be used,including fluorine compounds with carbonate structures, such as fluoroethylene carbonate, fluorine-containing vinyl carbonate,4-(2,2,3,3-tetrafluoropropoxymethyl)-[1,3]dioxolan-2-one,4-(2,2,3,3-tetrafluoro-2-trifluoromethyl-propyl)-[1,3]dioxolan-2-one,bis(2,2,3,3-tetrafluoro-propyl) carbonate,bis(2,2,3,3,3-pentafluoro-propyl) carbonate, or a combination thereof.Positive effect of fluorinated electrolyte additive on both anode andcathode materials has been observed.

Table 5 below shows the effect of fluorinated electrolyte additive (FEA)on the ion conductivity of electrolytes E03 and E07, which containdifferent ratios of common organic carbonate solvents such as ethylenecarbonate (EC), diethyl carbonate (DEC), and dimethyl carbonate (DMC)along with a suitable electrolyte salt. Appropriate electrolytes aredescribed in copending U.S. patent application Ser. No. 12/630,992 nowU.S. Pat. No. 8,993,177 to Amiruddin et al., entitled “Lithium IonBattery With High Voltage Electrolytes and Additives,” incorporatedherein by reference. It appears that reasonable amounts of fluorinatedelectrolyte additive do not significantly alter the ionic conductivityof the electrolytes, which is measured in milli-Siemens per centimeter.

The effect of FEA on E03 as base electrolyte in batteries with variousactive materials has been evaluated. The effect of 10, 15, and 20 vol %of FEA on silicon based Si-Gr electrode material has been evaluatedtogether with no additive sample (pristine) in batteries, using alithium counter electrode and the results are shown in FIG. 9. At allthree volume percentages, the additive has appeared to significantlyimprove the cycling performance of the batteries with silicon oxidebased materials compared to the sample with no additive. Similar effecthas been observed when silicon oxide composite was used and the resultsare shown in FIG. 10. The silicon oxide composite material is formedfrom HEMM at 300 rpm of silicon oxide and graphite followed by blendingwith a carbon source and heating at 900° C. to form a hard carboncoating to produce the SiO-Gr-HC composite material. FIG. 11 showed theeffect of 10 vol % FEA on HCMR™ cathode with lithium anode counterelectrode in batteries. FEA added battery has demonstrated higherspecific capacity and longer cycling life than the battery without theadditive. In general 10 vol % FEA additives showed the best stabilityand conductivity and was used as a standard amount in high voltageelectrolyte used in some of the following examples.

Example 3: Silicon Oxide-Graphite (SiO-Gr) Composites

Silicon oxide particles are HEMM milled with graphite to form a SiO-Grcomposite. The physical properties and cycling behaviour of thecomposites were evaluated together with untreated silicon oxide.

Pristine silicon oxide particles (Sigma-Aldrich-325 mesh) were mixedwith graphite at 300 rpm using planetary ball milling for threedifferent times t1, t2, and t3, with 1 hr<t1<t2<t3<24 hrs, in a drystate to form SiO-Gr samples. XRD measurements of the samples are shownin FIG. 12. XRD of the t1 sample comprises primarily of crystallinecarbon peaks. Longer time milling for t2 has led to the carbon to becomeless crystalline such that the amorphous SiO background becomes morevisible. At longest milling time of t3, an amorphous SiO-Gr compositehas formed with no observable crystalline carbon peaks.

As noted above, pre-milled silicon oxide showed improved electrochemicalperformance relative to pristine silicon oxide. So for the followingsamples, silicon oxide particles that had been pre-milled in ethanol fort5 hours at 300 rpm by HEMM were mixed with graphite at 300 rpm withHEMM ball milling for t4, t5, t6 or more hours to form SiO-Gr compositesamples (1 hr<t4<t5<t6<24 hrs). The composites were used to form fourelectrodes with loading densities between 2.25 to 3.29 mg/cm², which isused to build batteries with lithium counter electrode. Specifically,sample 1 composite was milled t5 hours and the loading density of theelectrode formed was 2.25 mg/cm². Sample 2 composite was milled for t6hours and the loading density of the electrode formed was 2.24 mg/cm².Sample 3 was milled for t5 hours and the loading density of theelectrode formed was 3.16 mg/cm². Sample 4 was milled for t4 hours andthe loading density of the electrode formed was 3.29 mg/cm².

FEA (10 vol %) has been added into the electrolyte used in the batterycomprising E03. The cycling performance of these batteries evaluated andthe results are shown in FIG. 13. The SiO-Gr composites havedemonstrated improved cycling performance compared to the untreatedsilicon oxide material.

Also, silicon oxide particles (55-70 wt %, Sigma-Aldrich, 325 mesh) weremixed with graphite (30-45 wt %) at 300 rpm with HEMM ball milling fort1 hr to form a SiO-Gr composite sample. The composites were used toform electrodes, which is used to build a battery with HCMR™ used as theactive material for the positive electrode. The battery was cycledbetween 4.5V to 0.5V after the first cycle charge to 4.6V, at a balanceof anode capacity to cathode capacity of 142% and the 1^(st) and the10^(th) cycles charge-discharge profiles based on cathode are shown inFIG. 14. The SiO-Gr composite has maintained about 85% of capacity atthe 10^(th) cycle compared to the 1^(st) cycle.

Example 4: Silicon Oxide-Hard Carbon Composites

This example demonstrates the performance of coin cell batteriesfabricated from electrodes formed from negative electrode activematerials comprising SiO-hard carbon composites (SiO—HC).

Composite precursor materials were prepared by ball milling. Inparticular, an appropriate amount of powdered silicon oxide particles(Sigma-Aldrich, 325 mesh) is subjected to ball milling for 1 hr to 24 hrat a milling rate of 300 rpm. For a given amount of silicon oxide, toobtain the appropriate amount by weight of carbon coating (3%-35%), therequired amount of carbon source is dissolved in tetrahydrofuran (THF)to form a solution. The ball milled silicon oxide particles is added tothe solution and mixed thoroughly for 2 hrs to 12 hrs with a magneticstirrer. The mixture is then dried over night to evaporate all the THF.The solid obtained is transferred into an alumina boat and heat treatedin a tube furnace between 700° C. to 1200° C. for 1 hr to 24 hr underargon atmosphere. The SiO—HC composite material is then collected andsieved.

A battery was assembled with an anode comprising the SiO—HC compositeacross from a high capacity HCMR™ cathode in a coin cell The anode wascoated with supplemental lithium to compensate for the first cycle IRCLof the anode. The cycling performance of the battery is plotted in FIG.15 showing 400 charge-discharge cycles, where cycle 1 is cycled at aC/20 rate, cycles 2-3 at C/10, cycles 4-5 at C/5 and cycles 6-400 at aC/3 rate. The first discharge capacity of the coin cell at C/3 is about235 mAh/g with a capacity retention of about 80% in 380 cycles.

Example 5: Effect of Pre-lithiation

The effect of SLMP™ on the charge/discharge profile and cyclingperformance of SiO-Gr-HC composite based anodes were studied and theresults are shown in FIG. 16 and the Tables 6 and 7 below.

SiO-Gr-HC composite was used to form an electrode with 3.7 mg/cm2density and supplemental lithium (SLMP™) on the 1.54 cm² electrode. TheSiO-Gr-HC composite based electrode was cycled against a HCMR™ cathodeand the results are shown in Tables 6 and 7 below for specific capacitydata obtained based on cathode active material mass or anode activematerial mass, respectively. Similar to the results obtained for SiO-Grbased electrode, the addition of SLMP™ on SiO-Gr-HC based electrode hasshown to increase the charge discharge capacity and increase the averagevoltage of the battery at different cycling rate. The charge-dischargeplots at a C/20 rate are shown in FIG. 16. The average voltages from theresults in FIG. 16 are 2.90V (pristine, 4.6V-0.5V), 2.94V (83%compensated, 4.6V-0.5V), 3.18V (100% compensated, 4.6V-1.V) and 3.63 (Lianode). It can be seen that the SLMP™ can effective eliminate the IRCLfrom the anode since results comparable to those obtained with a Lianode were obtained. The remaining IRCL can be attributed to thecathode.

TABLE 6 With Without Supplemental Li Supplemental Li Based on Cathode(4.6/4.5 V-2.0 V) (4.6/4.5 V-1.5 V) Avg. V-C/20 3.50 3.13 (1st cycle,4.6 V) Avg. V-C/10 (4.5 V) 3.465 3.14 Avg. V-C/3 (4.5 V) 3.42 3.10Charge Capacity-C/20 329 298 Discharge Capacity-C/20 268 214 ChargeCapacity-C/3 238 224 Discharge Capacity-C/3 225 183 Excess anode % 11%25%

TABLE 7 With Without Supplemental Li Supplemental Li Based on Anode(4.6/4.5 V-2.0 V) (4.6/4.5 V-1.5 V) Charge Capacity-C/20 1436 1443 (1stcycle-4.6 V) Discharge Capacity-C/20 1170 1036 Charge Capacity-C/3 (4.5V) 1039 1084 Discharge Capacity-C/3 982 886A small portion of the average voltage differences in performance notedin Tables 6 and 7 can be attributed to the difference in voltage ranges,but significant portion of the differences are due to the presence ofsupplemental lithium.

Example 6: SiO-Carbon Nanofiber (SiO—CNF) Based Composites

This example demonstrates the performance of coin cell batteriesfabricated from electrodes formed from negative electrode activematerials comprising SiO-Carbon nanofiber (SiO—CNF) based composites.

Carbon nanofibers (CNFs) were added to silicon oxide to enhance ratecapability and the cycling stability of the composite electrodes.Specifically, αSiO-εCNF (where 0.5<α<0.95 and 0.05<ε<0.50) is formed bymixing appropriate amount silicon oxide particles with carbon nanofibersusing a jar mill. The required materials were mixed in a plastic jarwith some zirconia milling balls. The jar was allowed to mix for onehour and the contents of the jar were collected for anode preparationprocess. There is no sieving step involved after the Jarmill mixingprocess.

The SiO—CNF composite negative electrode active material was formed intoSiO—CNF electrode as describe above. For comparison, pristine SiO powderwas also formed into SiO electrode. The cycling performances of thesetwo electrodes are evaluated in batteries with lithium foil counterelectrode described above and the results are shown in Table 8 below.The SiO—CNF battery exhibited significant improvement with capacityretention both at initial C/3 cycle and after cycling for 50 cycles.

TABLE 8 Specific Capacity Capacity at Initial Fade C/3 Cycle After 50Sample IRCL (mAh/g) Cycles SiO 33% 136 90% SiO—CNF 40% 1083 24%

Example 7: SiO—Metal Based Composite Materials with or without CNF

This example studies the performance of silicon oxide based compositeswith inert metal powders, as described above. A composite of αSiO-δMwhere 0.5<α<0.95 and 0.05<δ<0.55 was prepared by HEMM ball milling at aspeed of 300 rpm for 1-24 hr to form a first composite. An appropriateamount of carbon nanofiber (CNF) was added to the first composite andmilled for an additional 1-24 hours at 300 rpm to form a secondcomposite with αSiO-δM-εCNF where 0.5<α<0.9, 0.05<δ<0.35 and0.05<ε<0.50). FIG. 17 showed the XRD of SiO-M composite and SiO-M-CNFcomposite. No crystalline SiO-M was observed in either composite sample.

The SiO-M composite and the SiO-M-CNF composite were formed intoelectrodes and the electrochemical performances of the electrodes wereevaluated against lithium foil and the results are shown in FIG. 18. TheSiO-M-CNF based electrode appears to have improved IRCL and overallcycling specific capacity compared to SiO-M based electrode.

The SiO-M-CNF composite was also evaluated against HCMR™ cathode and theresults are shown in FIG. 19 and FIG. 20. The anode has a SiO-M-CNFloading density of 2.1 mg/cm² with supplemental lithium powder (SLMP™)lithium powder added on the surface of anode as described above and abalance of 150% anode capacity compared to cathode capacity. Theelectrolyte used in the battery comprised 10 vol % fluorinatedelectrolyte additive in the electrolyte. FIG. 19 showed the cyclingperformance of SiO-M-CNF based electrode against the HCMR™ cathodecalculated based on the weight of cathode active material. The sameHCMR™ cathode cycled against lithium foil electrode is also included forcomparison. The SiO-M-CNF based electrode appears to have comparablecycling performance as the lithium foil against the HCMR™ based cathode,maintaining specific cycling capacity above 225 mAh/g beyond 100 cycles.

The detailed charge/discharge profile of the SiO-M-CNF/HCMR batterybased on the weight of cathode active material was additionally shown inFIG. 19. FIG. 20 showed the cycling performance of SiO-M-CNF basedelectrode against the HCMR™ cathode calculated based on the weight ofanode active material. The SiO-M-CNF based electrode appears to maintainspecific cycling capacity above 1150 mAh/g after 55 cycles. Theirreversible capacity loss appeared to be 85 mAh/g (<200 mAh/g). Thecapacity retention after 50 cycles at a C/3 rate is 97%. FIG. 21 showscharge/discharge profiles for the 1st, 10th, 20th and 50th cycles of thebattery, indicating that it has comparable charge and discharge profilesat the 10th, 20th and 50th cycles.

A separate study was performed to evaluate the effect of milling on thesize of the particles and the results are shown in FIG. 22. Aftermilling at 300 rpm for 1-24 hours, the size of silicon oxide particlesis reduced significantly compared to the pristine sample, which isconsistent with the milling studies carried out in Example 1. The SiO-Msample showed similar size distribution after adding 10% CNF and millingfor additional 1-24 hours at 300 rpm to form SiO-M-CNF composites. TheSiO-M-CNF composite thus formed is studies with SEM at differentmagnifications and the results are shown in FIG. 23.

Example 8: SiO-Gr-HC—Si Composite with and without CNF

This example is directed to examining active material composites withboth silicon oxide and silicon. Silicon oxide milled at 300 rpm HEMM wascombined with nano amorphous silicon and graphite and milled for at 300rpm by HEMM. The resulting mixture is then carbonized at 900° C. for1-24 h in an Argon environment with the appropriate hard carbon source,such as poly vinyl chloride, poly(vinyl chloride)-co-vinyl acetate,polyacrylonitrile, glucose, sucrose, polymerized furfuryl alcohol,poly[(o-cresyl glycidyl ether)-co-formaldehyde resin,poly(methacrylo-nitrile), a combination thereof to form a compositematerial. XRD measurements of the composite material are shown in FIG.24, and these results reveal the formation of at least some crystallinesilicon in the composite. The resulting composite can be represented bya formula αSiO-βGr-χHC-φSi where 0.4<α<0.75, 0.05<β<0.25, 0.01<χ<0.20,and 0.01<φ<0.50. A portion of the SiO-Gr-HC—Si composite material wasthen mixed with CNF and jar milled to form a αSiO-βGr-χHC-εCNF-φSicomposite where 0.4<α<0.75, 0.05<13<0.25, 0.01<χ<0.2, 0.01<ε<0.2 and0.01<φ<0.5. Both the SiO-Gr-HC—Si composite and the SiO-Gr-HC—CNF—Sicomposite were formed into electrodes and cycled against a lithium foilelectrode and the results are shown in FIG. 25a . The SiO-Gr-HC—CNF—Sicomposite formed electrode appeared to have improved cycling performancecompared to the SiO-Gr-HC—Si composite formed electrode. TheSiO-Gr-HC—CNF—Si composite was additionally cycled against a HCMR™cathode and the results are shown in FIG. 25 b.

Two composite materials with varied amounts of SiO, Si, Gr, and HC weresynthesized: sample 1 has a composition with relatively less Si relativeto SiO and sample 2 has a composition containing higher siliconconcentration relative to SiO. Samples 1 and 2 had similar amounts of Grand HC. The cycling performance of electrodes formed from samples 1 and2 were tested against a lithium foil counter electrode and the resultsare shown in FIG. 25c . The sample with higher silicon ratio, sample 2,appears to have better cycling performance, maintaining specificcapacity above 1600 mAh/g after 60 cycles. All tested batteries had 10vol % fluorinated additive added to the electrolyte used in the battery.

The embodiments above are intended to be illustrative and not limiting.Additional embodiments are within the claims. In addition, although thepresent invention has been described with reference to particularembodiments, those skilled in the art will recognize that changes can bemade in form and detail without departing from the spirit and scope ofthe invention. Any incorporation by reference of documents above islimited such that no subject matter is incorporated that is contrary tothe explicit disclosure herein.

This document was prepared as a result of work sponsored by theCalifornia Energy Commission. It does not necessarily represent theviews of the Energy Commission, its employees, or the State ofCalifornia. The Commission, the State of California, its employees,contractors, and subcontractors make no warranty, express or implied,and assume no legal liability for the information in this document; nordoes any party represent that the use of this information will notinfringe upon privately owned rights.

What is claimed is:
 1. A lithium ion battery comprising a positiveelectrode comprising a lithium metal oxide, a negative electrodecomprising a silicon oxide based active material, and a separatorbetween the positive electrode and the negative electrode, wherein after50 charge-discharge cycles between 4.5V and 1.0V, the battery exhibitsat least about 750 mAh/g discharge capacity from negative electrodeactive material and at least about 150 mAh/g discharge capacity frompositive electrode active material at a rate of C/3.
 2. The lithium ionbattery of claim 1 wherein the silicon oxide based active materialcomprises silicon oxide with the structure of SiO_(x), 0.1≦x≦1.5.
 3. Thelithium ion battery of claim 1 wherein the silicon oxide based activematerial comprises a silicon oxide carbon composite composition.
 4. Thelithium ion battery of claim 3 wherein the silicon oxide carboncomposite composition comprises elemental silicon.
 5. The lithium ionbattery of claim 1 wherein the negative electrode further comprisespyrolytic carbon.
 6. The lithium ion battery of claim 1 wherein thesilicon oxide based active material has a volume average particle sizeof not more than about 8 microns.
 7. The lithium ion battery of claim 1wherein the negative electrode further comprises carbon nanofibers. 8.The lithium ion battery of claim 1 wherein the negative electrodefurther comprises graphite powder.
 9. The lithium ion battery of claim 1further comprising supplemental lithium corresponding to at least about10% of the negative electrode capacity.
 10. The lithium ion battery ofclaim 1 wherein after 50 charge-discharge cycles between 4.5V and 1.0Vat a C/3 rate, the battery exhibits at least about 800 mAh/g dischargecapacity from negative electrode active material and at least about 160mAh/g discharge capacity from positive electrode active material. 11.The lithium ion battery of claim 1 wherein the positive electrodecomprises a lithium metal oxide approximately represented by the formulaLi_(1+b)Ni_(α)Mn_(β)Co_(γ)A_(δ)O_(2−z)F_(z), where b ranges from about0.01 to about 0.3, α ranges from about 0 to about 0.4, β range fromabout 0.2 to about 0.65, γ ranges from 0 to about 0.46, δ ranges from 0to about 0.15 and z ranges from 0 to about 0.2 with the proviso thatboth α and γ are not zero, and where A is Mg, Sr, Ba, Cd, Zn, Al, Ga, B,Zr, Ti, Ca, Ce, Y, Nb, Cr, Fe, V, Li or combinations thereof.
 12. Alithium ion battery comprising a positive electrode comprising a lithiummetal oxide, a negative electrode, a separator between the positiveelectrode and the negative electrode, and an electrolyte comprisinglithium ions and a halogenated carbonate, wherein the negative electrodecomprises silicon oxide based active material and wherein the batterydischarge capacity decrease by no more than about 15 percent at the 50thdischarge cycle relative to the 7th discharge cycle when discharged at arate of C/3 from the 7th discharge to the 50th discharge.
 13. Thelithium ion battery of claim 12 wherein the silicon oxide based activematerial comprises a silicon oxide carbon composite composition.
 14. Thelithium ion battery of claim 12 wherein the negative electrode comprisessilicon oxide with the structure of SiO_(x), 0.1≦x≦1.5.
 15. The lithiumion battery of claim 12 wherein the electrolyte comprises from about 5volume percent to about 25 volume percent fluoroethylene carbonate,fluorinated vinyl carbonate, monochloro ethylene carbonate, monobromoethylene carbonate,4-(2,2,3,3-tetrafluoropropoxymethyl)-[1,3]dioxolan-2-one,4-(2,3,3,3-tetrafluoro-2-trifluoro methyl-propyl)-[1,3]dioxolan-2-one,4-trifluoromethyl-1,3-dioxolan-2-one, bis(2,2,3,3-tetrafluoro-propyl)carbonate, bis(2,2,3,3,3-pentafluoro-propyl) carbonate, or mixturesthereof.
 16. The lithium ion battery of claim 12 wherein the electrolytecomprises from about 5 volume percent to about 25 volume percentfluoroethylene carbonate, and wherein the negative electrode has aspecific discharge capacity of at least about 700 mAh/g at a rate of C/3based on anode's mass discharged from 4.5V to 0.5V.
 17. The lithium ionbattery of claim 12 wherein the negative electrode further comprisescarbon nanofibers.
 18. The lithium ion battery of claim 12 wherein thenegative electrode further comprises graphite powder.
 19. The lithiumion battery of claim 12 further comprising supplemental lithiumcorresponding to at least about 10% of the negative electrode capacity.20. The lithium ion battery of claim 12 the positive electrode comprisesa lithium metal oxide approximately represented by the formulaLi_(1+b)Ni_(α)Mn_(β)Co_(γ)A_(δ)O_(2−z)F_(z), where b ranges from about0.01 to about 0.3, α ranges from about 0 to about 0.4, β range fromabout 0.2 to about 0.65, γ ranges from 0 to about 0.46, δ ranges from 0to about 0.15 and z ranges from 0 to about 0.2 with the proviso thatboth α and γ are not zero, and where A is Mg, Sr, Ba, Cd, Zn, Al, Ga, B,Zr, Ti, Ca, Ce, Y, Nb, Cr, Fe, V, Li or combinations thereof.